SYNOPSIS OF A COURSE OF LECTURES.
CHAPTER I. History of SCIENCE in general, and MEDICINE in particular.
THE intentions of our forefathers in founding this College. The idea the Romans had of education evident from the origin of that word. The difference in the minds of men, not so much the effect of organization as education. The aptitude to understanding is a dead power in man, when not vivified by passions. The passion of glory, the commonly exciting cause. All men are susceptible of it in countries where glory conducts to power.* Reflections on the progress of civilization from the naked savage to polished humanity. Times and countries have their wastes and desarts. What form of government, and at what period most favourable to learning. [Page 2] Computation of the numbers of the human species destroyed in building up tyranny, by Sesostris, by Semiramis, by Xerxes, by Alexander, the Romans, the Sicilians, by Mithridates, the Goths and Vandals, the Crusadors, and by the Europeans on this continent.
The arts and sciences commonly flourish immediately after civil wars and commotions. Some of the most distinguished benefactors of mankind, when and where they lived—of those few who have aggrandized the human mind by cultivating their own.
Distribution of knowledge into particular sciences. PHILOSOPHY divided into the doctrine of the Deity—of Nature—and of Man. The doctrine of MAN divided into the doctrine of the body, and of the mind—and the doctrine of the union.
Of the intimate connection of all the sciences— the propriety of making the Muses all sisters.
The universe affords nothing so deserving our consideration and wonder as ourselves.—The human body, of all created things, most capable of relief; yet this relief most liable to err.
A classical investigation of the origin of the Healing Art. The fables of the antients pregnant with wisdom.
[Page 3]The antient poetry divided into (1) The Narrative—(2) The Dramatic—(3) Allegorical. From the allegorical the origin of medicine must be drawn. How the sciences were first taught by signs and symbols. As hieroglyphics preceded letters, so allegories preceded arguments,—various examples. This mode of teaching still among the Chinese, and in some degree among our Indians. The importance of a clue to these allegories, they having nature for their basis. How the symbols of ideas came to be taken for ideas themselves, truth came mixed with falsehood, human things with divine. Among all the ruder nations, the Priest, the Conjuror and Physician, were united in one man—other sources of superstition and nonsense—some traces discernable still in the Materia Medica.
Explanation of the allegory of Apollo or Phoebus: —Why called the God of Physic. The sagacity of the poets in making AEsculapius and Circe, brother and sister, and both children of Apollo.
An account of some of the Grecian Philosophers and Physicians who flourished during the period of Grecian liberty. Marcus Cato's opinion of them in his day.
[Page 4]Of HIPPOCRATES, why called the father of the Medical art—a specimen of his doctrine—a criterion by which his genuine works may be known —imitated by several, equalled by none—reflections on the age of the polished world, from the rich treasure of knowledge found in his writings —who first differed from Hippocrates—when and how Physicians were divided into sects—of the Dogmatic, Emperic and Methodic sects—account of Asclepiades, and his innovations in practice—his arts to acquire popularity and fortune.
An account of GALEN, wherein he did more harm than good to medicine, and acquired more fame than he deserved.
A short history of the various sects that flourished from this period to the time the Western Empire was overran by the Goths, and the Eastern by the Arabs.
How a northern swarm of barbarians extinguished the small light of learning that then remained, burning the libraries, universities and cities. Concerning Mahomet's conquests. From the 9th century to the 12th, the Arabians engrossed the province of physic, how far they enlarged its boundaries. In the 15th century Constantinople was sacked, the Greeks driven out, and forced to take refuge in Europe. The [Page 5] writers from this time called Moderns. Hence there appears three periods or revolutions of learning; one among the GREEKS, another among the ROMANS, and a third among the WESTERN nations of Europe.
MEDICINE, long cultivated on the coast of Malabar, derives its origin according to them, from the supreme God, and handed down for myriads of ages through the successive orders of inferior Deities;—reflections thereon,—a specimen of their theory. Of the state of physic in Mexico and Peru: their method of acquiring a knowledge of the healing-art more wise than any unlettered people yet known.
The revival or resurrection of letters. The nobles of all nations flocking to the holy war, admired the art and cultivation of the Greeks and Romans, shrunk back at their own barbarity—the consequences thence arising. How for several centuries the admiration of the knowledge of former ages retarded the advancement of science.
Elogium on ROGER BACON.
The discovery of the ARS ARTIUM OMNIUM CONSERVATRIX, the Art of Printing, and its immediate consequences.
The two systems of PHILOSOPHY prevalent at this period, viz.—The Philosophy of Aristotle, and the Philosophy of Plato: the first occupied [Page 6] the universities and cloisters. The poets, sentimental philosophers, and some others, were disciples of Plato. These two systems more or less discernable in all the writings of this period.
A great revolution in the theory and practice of Physic, by the introduction of Chymistry. An account of Paracelsus and his followers.
A short history of Medical Chymistry, in contradistinction to that very ancient art of smelting, refining and tempering of metals.
New diseases and new remedies, in consequence of a great part of the earth being discovered unknown to the ancients, viz. America,—the southern parts of Africa,—China and Siberia,—together with a vast number of islands.
In the 17th century HARVEY demonstrated the Circulation of the blood, which, together with the discovery of the Receptacle of the Chyle and of the Thoracic-Duct, overturned the whole system of Galen and the theory of the Chymists. GALILEO now introduced mathematical reasoning, and BACON his new mode of induction. This the aera of experiment in which several great men flourished.—Societies established for promoting and diffusing experimental philosophy in several parts of Europe with princes for their patrons.—Posts or conveyances by letter established. —Anatomy now prosecuted with juster views than [Page 7] before the discovery of the circulation.—Injections of coloured liquors first introduced.—The Microscope applied to investigate the more subtile parts of the body.
A catalogue of the most important anatomical discoveries from that time to the present.
General account of Theories from HARVEY to the time of HOFFMAN.
1. The Mathematical or Mechanical Theory, in which the blood was considered as the primum mobile of the whole body. How the consequences of this doctrine destroyed the principles on which it was founded.
2. The Theory of STAHL, who maintained that the rational and immaterial soul itself was the source of all the motions of the body.
3. The Theory of BOERHAAVE.
4. HOFFMAN's Theory, who maintained that so far was the body from depending on a state of the fluids as Boerhaave imagined, that the crasis of the fluids themselves entirely depended on the nervous power, and that the greatest part of diseases were affections of the nervous system.
General reflections on the foregoing history,— why it appears the history of opinions rather than of a progressive art.
[Page 8]An account of the few eminent authors in physic, in comparison of whom the rest are mere compilers.—Fewer books written on physic than any other branch of science of its extent.
On the simplicity of the medical art at present, compared with a century ago. By injections and microscopes, obscure things now rendered conspicuous, minute things magnified, and from confusion reduced to order and simplicity.
The more we know of any science, the greater number of particulars are we able to resolve into general ones, and consequently we shall be able to reduce its principles within narrower bounds.* This opinion verified by the present state of medicine.
The almost endless catalogue of diseases that afflict mankind a principal discouragement to students—how remedied.
SYDENHAM was the first who suggested the idea of reducing diseases to a certain determinate species, in imitation of botanic writers. Sauvages the first who attempted it.—Linnaeus—Vogel—Sagar and Cullen, the greatest improvers.
All scholastic teaching is classification,—exemplified in the division of the works of creation, first [Page 9] into the four elements, then into the three kingdoms. The animal kingdom divided into six classes, comprehending all animated nature; these classes divided into orders, each order into genera, each genus into species.
The CLASSES are marked by certain symptoms and circumstances which are common to each; the orders all agree in having the same marks with the class to which they belong, together with some additional ones peculiar to the order; the genera have all the marks and circumstances of the class and order, and besides have some which distinguish the genus; and the species have all the marks and tokens of class, order and genus, with the still further addition of symptoms or circumstances which give the specific character. See Encyclop. Brit.—also Lock on Human Understanding, vol. 1, p. 357, 8 vo. and vol. 2, chap. 3, on general terms.
All the known diseases that afflict mankind reduced to four classes, and these to 150 genera.*
The MATERIA MEDICA less advanced than any other branch of the art; the instinctive principle more exercised in what we take into the stomach [Page 10] than the rational, one cause. False Criteria another,—these reduced to eight heads.*
Mercury—Antimony—Opium—Peruvian-Bark, a few other Vegetables—Fire, Exercise and Water, include near all the physicians instruments.
Enumeration of the principal Desiderata in Anatomy—in the doctrine of the Animal oeconomy— in Surgery—and in the Therapeutica.
A view of the Data and Quoesita in the art of physic.
The general problem which comprehends the whole art is,—
Having the symptoms given to find the remedy; or thus divided,
(a.) Having the symptoms given to find the deviations of the body from its natural state.
(b.) Having this deviation given to find the remedy.
It is useful to invert these problems, and enquire,
(a.) Having the deviations given, what the symptoms must be.
(b.) Having the manner of operation of a successful remedy given, what the deviation must be. (See Hartley, vol. 1st.)
BOERHAAVE's method of studying physic—his idea of a consummate physician.
[Page 11]HOFFMAN's method, considered under four heads.
A rehearsal of Dr. CULLEN's objections to the Boerhaavian system.—How far he has supplied its deficiencies.
The out-lines of Cullen's Physiology, wherein he differs from all other medical teachers.
Elogium on BOERHAAVE.
General reflections on the various methods recommended in studying physic. Of the remarkable simplicity observable in the writings of the most successful enquiries after truth—several instances adduced.
Where did HIPPOCRATES, and other PRINCES in the art, study?—Wherever there were men and the concomitants of humanity, diseases and death, air, earth and water, all that surrounded them were the pages they studied!
CHAP. II.
SECTION I.
MAN, the object of our enquiries, includes within himself all the powers and qualities of nature, viz.—the mineral, vegetable, animal [Page 12] and intellectual; therefore has been called the Microcosmos.
Of the Res Macrocosmae, or every thing but man. These distinguished into (1.) Aliments, (2.) Medicines, and (3.) Poisons.
Concerning simple matter;—its astonishing divisibility, illustrated chemically and mechanically. The infinite divisibility of matter a mathematical truth, but a physical falshood? A little of the middle of nature known, its two extremes out of sight.
What led some philosophers to believe that all nature was animated. The imperceptible translations of inert matter to organized—from a vegetating body to the lowest order of animals.
Of the Zoophytes, or that class of beings which connects, animated and insensible nature.
On the SCALE of BEINGS.
The Universe a system whose very essence consists in subordination.
SYSTEMA NATURAE of Linnaeus briefly explained.
A connection between all ranks and orders by subordinate degrees necessary towards sustaining the magnificent fabric of the world. Wide distinctions made in the dignity and perfections of [Page 13] animals, little or none in their happiness. Concerning the various degrees of perfection, beauty, strength and understanding.
The animal produced by a cutting as in the Zoophytes, is but one degree above a vegetable,— that produced from an egg is a step higher,—that class of animals which is brought forth alive, still more exalted,—and of these, such as bring forth one at a time, the most compleat, the foremost of which stands the great master of all,*
MAN,—The knowledge of him reduced to six heads,—(1.) Physiologice, (2.) Diaetetice, (3.) Pathologice, (4.) Naturaliter, (5.) Politice, and (6.) Theologice. "Haec si noveris Homo es, et a relinquis animalibus, distinctissimum genus." LlNNAEUS.
"Man is a machine," Des Cartes.
Wherein the meanest animal is essentially superior to the most perfect result of human workmanship.
In proportion to the degradation of the animal in the scale of existence, the living and renovating principle is proportionably vigorous, various [Page 14] examples adduced; the same law observed in vegetables.
An effort towards a perpetuity of existence distinguishes the works of the Supreme Creator from the works of art.
Analogy between the instinctive or preserving principle in animals, and that approximating principle which binds together the terrestial globe, which guides the revolving planets in their courses, and keeps the material system from dissolution.*
Man is a being compounded of body, spirit and soul, or Corpus, Vis Actuosa et Mens.
The BODY first offers itself to view—considered collectively as one mass, consists of (1.) Earth, (2.) Oil, (3.) Water, (4.) Salt, (5.) Phlogiston, and (6.) Mephitic air. Considered entire, and particularly its exquisite form and wonderful faculties, place it at the head of the visible series. Amidst the exact harmony of parts and actions, there exists a perpetual conflict; by this conflict the body is supported; that action which is the life of the body is also the cause of its death.
From which view this inference is unavoidable, namely, the most perfect being we know of, depends on a SUPERIOR BEING who created and supports its existence.
SECTION II.
THE actions of the human body distinguished into VOLUNTARY, INVOLUNTARY and MIXED.
The involuntary, or instinctive movements, are exercised in preserving the body, and are, more strictly speaking, the animal oeconomy.
The appetites and actions on which our very existence depends, are not left to the fallible reason, or caprice of man.
The instinctive actions varying in different stages and circumstances of life, are strong in proportion to their importance:—various instances adduced.
All this depends on a principle which some call VIS ACTUOSA, others IMPETUM FACIENS, others ARCHAEUS. This power is innate, and is that, by which man lives, it forms him, it nourishes him, refreshes him, pathetically affects him, moves him, animates him; by it he feels, he desires, refuses, sleeps and wakes: nevertheless it is totally different from the mind, for,
In the body, guarded by the Autocratea, or VIS MEDICATRIX NATURAE is found something of quite a different nature from what has been mentioned;—a power of thinking, reflecting, comparing, chusing, and representing to itself [Page 16] past, present, and to come. This power in relation to its several operations, is termed comprehension, understanding, reason, mind, will, freedom, or collectively by the single word SOUL.
This immaterial thinking part of man, is so connected with the material and corporeal part of him, and particularly with the nervous system, that motions excited in this, give occasion to thought; and thought, however occasioned, gives rise to new motions in the nervous system. This mutual influence we assume with confidence as a fact, but the mode of it we do not understand.*
The opinion of THALES concerning the immaterial thinking part of Man—of PLATO—of PATHAGORAS and of HIPPOCRATES.
The Cartesian Hypothesis—the opinion of some of the Chemists, of the THEOSOPHI, particularly MALBRANCHE. The system of LEIBNITZ and WOLFE,—of BAXTER and PRIESTLEY.—All abounding with unsurmountable difficulties.†
SECTION III.
ON the original construction of the animal Solids.—Do they consist of streight fibres or threads, as Boerhaave taught; or fibres and laminae forming the Tela Cellulosa, as Haller supposed? Or are they spiral, convoluted and interwoven with one another?
The construction, extent, and nature of the Tela Cellulosa.—On the living, or vital Solids.
All the organical parts of the human body maintained in the power, or fitness for acting either successively, or simultaneously by two forces or springs, viz. (1.) The BRAIN and it's appendages the nerves. (2.) The HEART and it's appendages the Blood-Vessels, mutually exciting each other like the main-spring and regulator in a Watch. —These movements, in order to be perpetual and regular, require to be as perpetually and regularly wound up, and this is done by the FOOD taken into the stomach and there digested.
The Brain and Nerves may be considered as forming one system. The Heart and Blood-Vessels another. The Stomach, Intestines and assistant Chylopoetic Viscera form a third. The Lacteals, the common Lymphatics, and the Conglobate-Glands form a fourth. May not the Systema spiritale pneumonicum be considered as a fifth?
[Page 18]From these five fountains all the actions of the body, and all the power which it exerts, are derived.
Although each organ or system of the human body, has an action peculiar to itself, yet are they all actuated by one individual life. *
Human life or health, is the sum or aggregate of all these actions and functions, which cannot therefore be derived from the brain alone, or heart, or stomach—or absorbent system—or the pneumonic, but from the conspiration of all of them; hence emerges the sympathy of parts. †
These subjects are so involved in each other, that it is impossible to begin any where on clear ground, or so as to proceed from the Data, to the Quaesita: begin where we will, we always find some things necessary to be premised, which are not as yet demonstrated.
CHAP. III. Of particular Organs and Functions.
SECTION I. Of the Heart and Blood-Vessels.
THE heart of man consists essentially of two cavities, there being two hearts, strictly speaking, joined together in the human body, [Page 19] serving for two circulations of the blood, one through every part of the body, and one through the lungs.*
Of the AURICLE.
Of the VENTRICLE.
Of the VALVES.
Origin, general structure, and distribution of the Aorta.
From the ultimate branches of the Aorta arise tubes which terminate in the heart, joining together as they go on towards it, forming principally two large tubes, which open into the right Auricle:—these are called,†
VEINS,—their general structure.
In all the veins perpendicular to the horizon, excepting the Uterus and Porta, there are small valves, but none in the deep running vessels of the Viscera—none in the Lungs, Brain, Liver, or the whole system of the Vaena Portarum—nor in any blood-vessels, less than the twelfth of an inch, diameter.‡
How do the veins begin? There is a structure between the veins and arteries little understood.§
The blood-vessels in a live animal are always full.
[Page 20]When an animal dies, the Arteries and Veins loose their cylindrical form and are flattened, and the capillaries contain less blood, so that the blood sufficient to fill the vessels when the animal was alive, is not capable of filling them after he is dead; therefore the arteries, veins and capillaries of the living animal, are commonly contracted to a greater degree than they can be by their elasticity.†
The elasticity is commonly endeavouring to distend them, but is always overpowered by the contractile power depending on life, which adapts the size of the vessels to the quantity of blood contained in them.
If the vessels are emptied to such a degree that they cannot adapt themselves to the blood, and continue cylindrical, the animal dies.‡
On the Vis Vitalis.
APHORISM I. ALL the living parts of the body have, besides those attributes common to all bodies, as solidity, extension and gravity, a peculiar something which distinguishes the living from a dead body.
A muscular fibre will contract, and that not by the power of gravitation, cohesion, chrystallization, (electricity?) magnetism, or chymical attraction.
[Page 21] APH. II. This property in animal bodies has been in a great measure overlooked by some teachers of great reputation, and totally neglected by others.
APH. III. Whatever by its contact with an animal fibre, excites in it a contraction or oscillation, we call a Stimulus.
APH. IV. That state of an animal fibre in which a contraction or oscillation is produced by the contact of a stimulus, we call Irritability.
APH. V. That principle in animals, on which sensation, motion, and all the animal powers depend, we call the VIS VITALIS.
APH. VI. If by the application of a stimulus to the solids, a perception is excited in the mind, this effect we call sensation or facultas sentiendi.
APH. VII. By the action of stimuli on the solids, the Vis Vitalis is excited and preserved; when diminished, it may be encreased, and when totally suspended, it may be restored.
[Page 22] APH. VIII. Without heat as an exciting and preserving stimulus, vegetable and animal life cannot be supported. Thus the hatching of eggs is the effect of the application of a particular degree of heat, without which the egg remains inanimate. The same application to an animal, or part of an animal consolidated by frost, will re-animate it, or restore the Vis Vitalis.
APH. IX. Different animals, and the various parts of the same animal, have different degrees of irritability.
APH. X. The denser, or more compact the solids of an animal, or parts of an animal, the stronger and less irritable is the animal or parts of the animal. Thus the muscles are in a great degree irritable, but their irritability lessens as they become tendinous, and is in a manner lost when ossified.
APH. XI. On the contrary, when by inflammation the fibres of the least sensible parts are elongated, and the cohesion of their constituent corpuscles diminished, their irritability and sensibility is proportionably encreased until it arrives at the extreme, when the sensibility and irritability diminishes until it is lost, and a dissolution takes place.
[Page 23] APH. XII. Experiment teaches us, that the Heart is endowed with irritability above most other parts. Even when the heart is taken out of the body, and in some animals though it be cut in pieces, it can be excited to motion by proper stimuli*.
SECTION III.
Nature and Properties of the Blood.
THE various substances used for food, are converted by the organs of digestion into chyle, and afterwards into blood.
FROM this red mass all the other fluids are formed. The constituent parts of the blood unknown till the time of Monsieur Senac.
THE blood consists of (1.) The serum. (2.) Coaguable Lymph. (3.) The red part, and (4.) The superfluous water. The nature, properties, and mode of mixture in each. Little or nothing to be known from the chymical analysis of the red mass.
Leuwenhock's idea of the red gloubles erroneous. Necessary to know the fallacies of optics before their shape can be determined.
[Page 24]Is the blood an inanimate fluid, or is it a live?
Must the blood be converted into a solid part of the body, before it can feel?
Where is the first communication between body and mind?
Does the albuminous fluid incessantly passing through the Lacteals into the blood, only require the heat of the blood-vessels to vivify it like incubation, by the warmth of the Hen; or is its animation reserved for the lungs?
Arguments for and against the celebrated J. Hunter's hypothesis of the life of the blood.
The red part of the blood, soluble in water, but not in serum, capable of undergoing the putrefactive fermentation; this fermentation, distinguished into three stages; the process described, part of the blood goes to form the various fluids; part to repair the waste of the solids; and part is destroyed and thrown out.
The fluids of animals are formed and destroyed by fermentation. What we mean by FERMENTATION.
Putrefaction defined—consists of two fermentations.
A portion of the blood is constantly destroying. Is it by what we call putrefaction?
[Page 25]The evident evacuations from the blood, are (1.) From the skin by evaporation. (2.) From the surface of the lungs. And (3.) by the kidnies.
Of the grand Antiseptic of Animal Bodies.
Some uses of the blood, besides those commonly noticed.
Of the actions of the small vessels when divided by a small wound. How in consequence of a slight inflammation, they throw out a new fluid, in order to effect a reunion. This uniting medium, that part of the blood called the Coaguable Lymph.
Is not inflammation a process of the animal oeconomy, to supply an injured part with Coaguable. Lymph? Several phenomena related to countenance this idea.
On the formation and use of Pus.
What is the alteration in the vessels of an inflamed part, producing pus? How far is it a regular secretion.
Of the gloubles of pus, as they appear through the microscope.
The opinion that the solids go to the formation of pus, erroneous.
The intention of pus is not to destroy, but to defend and preserve the parts.
[Page 26]Of the motion and circulation of the blood, and of the several organs and actions employed in supporting it.
Of the circulation in the Foetus—in Amphibious Animals, and in Scaly-Fishes.
Of the Lungs.
Anatomical Description of that set of vessels in the Lungs, which contain AIR, and those which contain BLOOD.
Is the blood in the pulmonary arteries incapable of nourishment, or must its yet crude chyliferous particles complete the circle of the system, before it can nourish?
Of the secretions from the vessels of the Lungs —of the nerves of the Lungs, with their peculiarities.
How respiration is performed in Man—how in Birds—in some Reptiles, and in Insects. The reason Snakes can live in an exhausted receiver, and Insects exist in compact bodies.—How respiration is performed in amphibious Animals and Scaly-Fishes.
How the blood circulates in the Child in the Womb.
Nature and properties of the AIR we commonly breathe.
[Page 27]On the PULSE.—Scarce any two authors use the same terms to express the same pulse. Several passages of Hoffman, Silvius, Etmuller, Decker, Scheldhammar, Bellini, Boerhaave and Prosper Alpinus, compared.
SECTION IV. On the Heat of the Human Body.
HOW far does the heat of animals depend on the motion of the blood? Is the heat owing to the nervous fluid, or AEther, or Electricity, or Phlogiston?
The power, whatever it may be, which produces, maintains and regulates the heat of the human body in health, produces HEAT when the surrounding substances are heated to a less degree than 98 degrees of Farenh thermometer; and COLD, when they are heated to a greater degree*.
SECTION V.
Of the Stomach and assistant Chylopoetic-Viscera.
ANATOMICAL description of the Stomach and alimentary Canal; peculiarity in the distribution of the vessels of the Stomach and Intestines.
[Page 28]The Stomach performs two distinct offices; the first, digesting the food; the second, communicating fresh life and vigour to the remotest parts of the system. HIPPOCRATES opinion of this wonderful organ.—The opinion of ARETAEUS CAPPADOX, of HELMONT, of SYDENHAM, of FOTHERGILL.
No organ merits so much attention as the Stomach,—no function of such importance to the Physician, as digestion.—The feeling and affections attributed to the heart, belong to the Stomach. No part of the body capable of so many different feelings. On the Stomach in a great measure depends the whole man,—various examples adduced.
Of the consent between the skin and the Stomach.
A state of distention or erection in the ultimae vasculae or villi of the nerves necessary to free perspiration—this distended or collapsed state is somehow connected with a sound or unsound Stomach?
On Digestion.
Systems relative to this function.
(1.) BOERHAAVE's, which supposes two principal agents, viz.—the different fluids collected in the [Page 29] Stomach—and its mechanical action. The secondary agents are, (1.) heat, (2.) air, (3.) the nervous fluid, and (4.) an incipient fermentation.
(2.) SIR JOHN PRINGLE's and DR. M'BRIDE's theory, who suppose it a fermentative process. Fermentation divided into three stages. Chymical Analysis of the gastric fluid; found to be neither acid, nor alcaline, but neutral.
Experiments in Papin's Digester, not applicable to the human Stomach.—The amazing power in the cold Stomach of some Fishes, sufficient to overturn the system that supposes heat the grand instrument of digestion.
The amazing pressure of the Stomach as calculated by DR. PITCAIRN and others, entirely without foundation.
The Experiments of SPALLANZANI.
How digestion is performed in animals with muscular Stomachs, as common fowls, turkeys, pigeons, &c. Their food triturated previous to digestion, by muscles called gizzards. The action of the gizzards upon sharp pointed metallic bodies.—Anatomical description of the Oesophagus and gizzards of fowls.—Of the Crop, its glands, cartilaginous coat and excretory ducts.
[Page 30]How digestion is performed in animals with intermediate stomachs; what we are to understand by intermediate stomachs. Experiments proving that in such animals, digestion is owing to the gastric fluid alone.
How digestion is performed in the reptile tribe; quicker accomplished in warmer seasons. During their torpid state, flesh may remain in their stomachs for months without putrefying.
How digestion is performed in scaly fishes.— Anatomical description of their stomach and intestines. Their stomachs remarkably cold, with no possibility of triture. Some fish digest crabs, lobsters, shells and all. The bottom of their stomachs digests substances sooner than the upper part. This solvent power greater in the stomachs of fishes than any other creature we know of; few animals can digest an entire live animal. In fishes the gastric fluid alone dissolves the small live fish they swallow.
The process of digestion in sheep, oxen, and other ruminating animals;—wherein their stomach and bowels differ from man's. How digestion is performed in birds of prey—anatomical description of their digestive organs, their stomachs approach near to the human; have a double pancreas.
[Page 31]Result of experiments on the gastric juice of birds of prey; it will not dissolve vegetables, even if boiled, yet their stomachs dissolve the hardest bones. Digestion in birds of prey proved to be owing to the gastric fluid alone.
General observations on the gastric fluid of animals. Does not freeze so soon as a solution of salt, or of simple water. The human gastric juice exposed for weeks in the hottest seasons, suffers no change of colour, taste or smell. The gastric juice of birds of prey, dissolves flesh out of the body, sooner than the process of putrefaction.
Flesh given to a sick bird of prey, found unaltered.—Teeth given to the same class of birds, the fangs dissolved, the enamel untouched! Horns and tanned leather indissoluble—the Tendo Achillis of an ox dried, perfectly soluble. Raw flesh and other substances, dissolved when tied up in a linen, and even in a broad-cloth bag, and thrown into the stomach of an eagle.
The process of digestion in animals with membranous stomachs. This class comprehends the inhabitants of salt and fresh water; Amphibious animals, as the tortoise, frog, water-snake, &c. Reptiles, as the viper, land-snake, &c. Quadrupeds, [Page 32] as the horse, ox, cat, dog, &c. Also, birds of prey, as the eagle, owl, &c. And lastly, MAN himself.
Of the advantages of comparative anatomy and analogical reasoning. Analogical arguments probable, but not conclusive. How plausible inferences from well known facts in brutes, occasioned many errors respecting man.
In some animals trituration of the food is necessary—in man it is done by the teeth—in gallinaceous fowls, by the gizzards.
In frogs, serpents, birds, and fish of prey, no trituration takes place.
Wherein man's digestive faculties differ from all other animals.
Man is OMNIVOROUS.
Of the coaguable liquor of the human stomach— Of the runnet in calves—The inner coat of the stomach of gallinaceous fowls, has the same property—Those with intermediate stomachs possess it likewise. The stomachs of various reptiles, and several scaly fishes, have the faculty of curdling milk.
Is this coagulating property inherent in the internal coat, or is it owing to the gastric fluid!
To imagine that nothing but acids coagulate milk, is to measure nature by our own narrow [Page 33] prejudices? The blood of a certain animal will not coagulate milk, but pieces of the heart, liver, lungs, and some other parts of the same animal, will.
RECAPITULATION. The succus gastricus differs from all known solvents of art or nature. It is at once, an antiseptic and solvent. In some quadrupeds, in some birds of prey, it actually sweetens putrid flesh in less than two hours.
Wherein the succus gastricus essentially differs from the Saliva; hence the fallacy attending Pringle and M'Bride's conclusions. The result of various experiments made by Reaumur, Spallanzani, J. Hunter, Stevens, and others, only confirms the opinion advanced two thousand years ago, by HIPPOCRATES.
If digestion is well performed, the chyle is proper, be the food ever so various; the blood from the chyle natural—the secretions—nutriment— and excretions, regular;—health, strength, and activity, will ensue—disease vanish. If digestion languish, the contrary happens, be the food what it may, unless the injured faculties of digestion, be restored to their pristine and natural state.*
On the food of Man.
ALL the food used by mankind consists of [Page 34] farinaceous, or mucilaginous vegetable substances or native vegetable acid—or sugar or expressed oil, or animal solids, or animal fluids, containing a mucilaginous matter—all traced ultimately to vegetables and water.
A view of the TERRAQUEOUS GLOBE. Of the CIRCULATION between the ocean, the atmosphere, and earth. The whole terraqueous globe, sea as well as land, together with the whole region of the atmosphere, happily contrived to afford sweet and running waters, all of which have a reference to the original food of man, VEGETABLES.
VEGETATION traced from the sowing of the seed, to the formation of the root—the trunk—the branch—the flower—the fruit—and last of all, to the seed again.
THE SEXUAL SYSTEM OF BOTANY, briefly explained.
Analogy of vegetables to animals.
CHAP. IV. Structure, Course, and Oeconomy of the VALVULAR LYMPHATIC SYSTEM.
THE ABSORBENT SYSTEM consists of (1.) the Lacteals. (2.) The Common Lymphatic Vessels. (3.) The Thoracic Duct. And (4.) the Glands, [...]
[Page 35]A Lymphatic, is a fine pellucid tube nearly cylindrical, divided by valves, so as to have the resemblance of joints.*
History of their discovery.
The Lacteals begin from the intestinal tube, and may with propriety be called the Lymphatics of the Intestines, they begin with open mouths, in almost every part of the body, as they do in the intestines.
The fluid they contain is colourless, like water; the course of their fluid is from the extreme parts of the body to its center.
The coats of the Lymphatics have in common with other parts, arteries, veins, and nerves.
The Lymphatic System in most animals, † but particularly in man and quadrupedes, is full of valves.
Description of the Conglobate or Lymphatic Glands. The Thoracic Duct, is a lymphatic of the largest order: it begins near the Diaphragm, and commonly terminates in the left subclavian vein; to it, as the common receptacle, the whole lymphatic system tends.
In passing on towards the heart, the lymphatics enter the conglobate glands—the manner [Page 36] described. Haller's opinion of the absorbing veins, erroneous. As the arteries are evidently connected in structure and office with the Lacteals or Lymphatics of the intestines, may they not in like manner with all the rest in the system? Experiments rendering it highly probable that the Thoracic Duct is not the general or only termination of the Lymphatics. Has the Brain Lymphatics? Arguments for and against this opinion. Absorbent glands found in the foramen caroticum in the basis of the skull. Why are the glands of the neck more numerous in man than in any other animal?
On the action of the absorbents: objections to their acting on the principle of Capillary, tubes according to Haller and others—a particular stimulus required. (See Vis Vitalis, p. 21.)
An explanation of their action attempted— The probability of every living body absorbing.
THE USE OF THE ABSORBENT OR LYMPHATIC SYSTEM.
The Lymphatics are the Modulators of the nutritive or arterial system. The Lymphatics and arteries are perpetually counteracting each other.*
[Page 37]The Lymphatics take in our food—They prepare several secreted liquors. The Lymphatic glands, guard the system from poison by their inflammation and pain.
The Lymphatics take up the solids as well as the fluids of the body, proved by experiment— they eat off the roots of teeth in children, and absorb the alveolar processes after the teeth drop out in old men. The separation of a mortified part is by means of the absorbents. Their action further illustrated in diseases of the bones. The absorbents regulate the quantity and quality of the chyle.
Does the lymphatic system in certain diseases, where the patient cannot take food into his stomach, absorb the fat to support the system? Observations on animals that sleep all winter.
On favourable and unfavourable surfaces for absorption: An ulcer more favourable to absorption than an inflammed part.
Does the presence of one infectious matter prevent the absorption of another?*
On the good effects of introducing morbific matter by a different rout from what it would naturally take, as in inoculation. Can two infectious diseases act on the body at the same time?*
The absorbent system more active after sleep.
Miscellaneous observations.
CHAP. V. Nervous System.
THE BRAIN is that soft whitish mass which sills the cavity of the skull, and is immediately surrounded by two membranes, called Meninges by the Greeks, and Matres by other ancients: one is very strong, and lies contiguous to the skull; the other is very thin, and immediately touches the brain. The first is called Dura Mater, the last Pia Mater.
The brain is furnished with blood-vessels in the same manner as the other parts, excepting that larger arteries anastomose, and the smaller veins enter more suddenly into a larger trunk, whose sides are of a firmer texture†.
In the more perfect or complicated animals, it is contained in the cavity of the skull:—in the less perfect, it is diffused all over the body.
In man, the brain is in a larger proportion to the whole body than any other quadruped, or any bird, or fish hitherto known†.
From the white part, masses of fibres arise, which go to every part of the body. These are called Nerves †.
[Page 39]But so ignorant are we of the origin of the nerves, that the lowest in the spinal marrow may, for ought we know, come from the top of the brain.
One large mass passes down through the cavity of the spine, and is called the spinal-marrow†.
The brain, spinal-marrow and nerves, are covered with membranes of a very firm texture. The nerves sent to the organs of the senses, there lose their firm coats, and terminate in a pulpy substance.
Of the connexion and dependence of the nerves on the Hydraulic part of the machine.
A general view of the Nervous System‡.
The nervous system, as the organ of sense and motion, is connected with so many functions of the animal oeconomy, that the study of it must be of the utmost importance, and a fundamental part of the study of the whole oeconomy.
The nervous system consists of the medullary substances of the brain, cerebellum, medulla oblongata and spinalis, and of the same substance continued into the nerves, by which it is distributed to many different parts of the body.
[Page 40]The whole of this system may be distinguised into four parts—
I. The medullary substance contained in the cranium and vertebral cavity; the whole of which seems to consist of distinct fibres, but without the several fibres being seperated from each other by any evident enveloping membranes*.
II. Connected with one part or other of (§ I.) are the nerves, in which the medullary substance is contained; but here more evidently divided into fibres, each of which are seperated from the others by an enveloping membrane derived from the Pia Mater.
III. Parts of the extremities of certain nerves (§ II.) in which the medullary substance is divested of the enveloping membranes from the Pia Mater, and so situated as to be exposed to the action of certain external bodies, and perhaps so framed as to be affected by the action of certain bodies only: these we call the sentient extremities of the nerves.
[Page 41]IV. Certain extremities of the nerves (§ II.) so framed as to be capable of a peculiar contractility; and in consequence of their situation and attachments, to be by their contraction capable of moving most of the solid and fluid parts of the body. These are named moving or muscular fibres.
That muscular fibres are a continuation of the medullary substance of the brain and nerves, has not been shewn by Anatomists, nor universally admitted by Physiologists; but we now suppose it, and hope afterwards to render it sufficiently probable.
Are the Ganglions of the nerves to be considered as a part of the nervous system distinguished by a peculiar function?
These several parts of the nervous system, are every where the same continous medullary substance, which we suppose to be the vital solids, so constituted in living animals, and in living systems only, as to admit of motions being readily propagated from one part to every other part of the nervous system, so long as the continuity and living state of the medullary substance remains.
In the living man there is an immaterial thinking substance or MIND; and every phoenomenon of thinking is to be considered as an affection or faculty of the mind alone. But this immaterial [Page 42] and thinking part of man, is so connected with the material and corporeal part of him, and particularly with the nervous system, that motions excited in this, give occasion to thought; and thought, however occasioned, gives rise to new motions in the nervous system.
It is probable that the motions excited by the application of stimuli to a moving and irritable part, or to the nerve going to a moving part, do not arise in the brain, but immediately in the nerves, or in the part; the brain, in this case, only keeping up the life of the part, and rendering it capable of motion*.
A substance may act on one part as a stimulant or sedative, and have a less effect, or none at all, when applied to another, although otherwise equally irritable. Such stimuli are called specific ‖. (See the aphorisms on the Vis Vitalis.)
It has been conjectured by some, that motion was communicated to parts by a fluid flowing through the nerves as tubes; by others, that it was communicated by vibrations§, and by others, that it arises from electricity.
Is a nerve a better conductor of electricity than any other part in the same state of moisture? [Page 43] By a moderate pressure the nervous influence is intercepted.
Natural History of the Torpedo.—The organ which is said to collect the electricity in this animal is not its brain, which is remarkably small.
Reason and Instinct compared.
REASON is a self-improving power or faculty of the mind.
INSTINCT is that discretion which in different degrees is diffused through every animal, directing them to choose what is good, and to avoid what would be destructive to them. It attains its perfection at once, and is most apparent where reason is weakest.
On Custom and Habit.
Custom is the frequent repetition of any application to the body, capable of affecting the sensible or irritable parts; or it is the repetition of any action or motion of the body*.
Habit is the effect of such repetition.
On EXERCISE, REST, and SLEEP.
CHAPTER VI. On the PRIMORDIA OF ANIMALS.
THE GENERATION of animals has excited the curiosity of Philosophers and Physicians [Page 44] from the time of ARISTOTLE to the present; still it is involved in impenetrable darkness.
There are facts sufficient to entirely destroy the two famous systems of the Epigenosists, and the Vermiculists. It is, moreover, a vain and useless speculation: the two extremes of nature, the very great, and the very small, are out of sight; from the grandeur of the one, and the subtilty of the other, Admiration itself is soon overpowered, and sinks into undiscerning amazement!
Quomodo ignoras quod venti vestigium, qualia sint in Proegnantis Utero ossa: sic DEI opus ignoras qui facit omnia! ECCLESIASTES, chap. xi. ver. 5.