tion.

Introduc- larly to the state of vitality, and as they are found in every object that exists. These latter are subject to the general laws of matter, are confounded with the phenomena of universal nature, and may be denominated physical phenomena. Among the former, some are confined to the arrangement or disposition of the parts in organs, and depend on the structure or form of these organs. These may be called organic phenomena. Others depend on the particular laws that govern vital beings, and are not the result of any peculiar organization; these are vital phenomena.

14

Observation.

15 Experi

ment.

16

Cautions.

די

Modern arrangements.

18 Two modes

ment.

Observation alone is sufficient to indicate the presence or the existence of these phenomena; but to unveil them fully there is required an unceasing attention, that is resolved to pursue them through the changes produced by age, sex, climate, situation, and all those circumstances that can affect the living system.

To observation, he must add, wherever this can be done with a chance of accuracy, a patient investigation of nature by experiment. From the experiments of Spallanzani and Stevens on digestion; of Goodwin, Menzies, Spallanzani, and Davy on respiration; of Monro, Galvani, Volta, and a hundred others on animal irritability, with many other experiments made both at home and abroad, more light has been thrown on the economy of living bodies, than by all the hypotheses and theories that the most ingenious speculatists have contrived since the first dawn of infant science.

In following out Bacon's great plan of observation and experiment, we must, however, take care in physiological, as in all other physical inquiries, not to be too hasty in our conclusions, and not to suppose that we have reached the bottom of the well of truth, when we have barely got within its verge. Further observations on this subject are unnecessary here, as we have already treated it at some length in the articles PHILOSOPHY and PHYSICS.

We shall conclude these introductory remarks with a brief sketch of the principal arrangements of modern physiologists, and a tabular outline of the subject as we propose to treat it in the following pages.

There are two modes of arrangement that have usualof arrange-ly been adopted in treating physiology; one according to the order of the functions, and another according to that of the organs by which these are performed. The latter of these was adopted by Haller; the former is that of Dumas, Cuvier, and most of our later physiologists.

19 -Arrange

ment of
Dumas:

Dumas, after a long introductory discourse, in which he treats of the best method of pursuing the study of anatomy and physiology, divides his subject into six parts. In the first of these he offers some general views respecting anatomy, physiology, and all the branches of physics which are employed in illustrating the nature and properties of organized and living beings. In this part he gives a compendious history of the progressive improvements in anatomy and physiology, points out the relations that take place between these sciences, and the auxiliary branches of mathematics, mechanical philosophy, chemistry, and natural history; he considers the principal differences that distinguish organized from inorganic matter; the nature, effects, and duration of life, and of the general and particular powers or faculties of nature, both in living and brute matter.

In the second part he lays down the fundamental principles on which the physical constitution and par

tion.

cular economy of man depend; treats of man consider- Introve ed individually; of his formation, structure, and varieties; of the modifications produced in the nature of man by age, sex, habit, and temperament; of the relations between man and external objects; of the action and reaction of the organic systems on each other; of the organic structure of man, and of its several varieties in the different parts and organs; of the natural composition of the different fluids and solids of the human body: and gives a methodical division of the functions, with a critical examination of the modes of classification commonly received.

In the third part he treats of the plienomena of the animal economy, in the relation which they bear to the perpetual commerce established between man and the organs that surround him, or of sensation and motion. Here he considers the action of external objects upon man, whence result the phenomena of sensation, and the action of man on external objects, from which arise the phenomena of motion.

In the fourth part he treats of the phenomena of the animal economy, in the relation which they bear to the consistence of the fluids, the cohesion of its solids, and the temperature of the whole system. Here he considers the mutual action between the vessels and the blood, from which result, both in the solids and fluids, that degree of cohesion and pliability that favours the necessary expansibility of the living body, or the function of circulation; the action of the air, and of caloric, on the solids and fluids, from which results the degree of expansion necessary to life, or the function of respiration.

In the fifth part he treats of the phenomena of the animal economy in the relation which they bear to the healthy and entire state of the material substance and composition of the body. Here he considers the action of alimentary substances on the human body, in repairing its loss, and preserving its substance, from which result the phenomena of digestion, absorption, and nutrition; and of the action of certain organs on the fluids of the body, in separating those which do not serve the purposes of nutrition, from which result the phenomena of secretion and excretion.

In the sixth and last part, he treats of the phenomena of the animal economy in the relation which they bear to the commerce established between the individual and the species. Here he considers the mutual physical action of the two sexes, from which arise the phenomena of generation; and the mutual moral action of several individuals, from which result the phenomena of speech, and mutual intelligence.

From this sketch of the arrangement of Dumas it will be seen, that although he takes a very extensive view of the subject, his observations are chiefly confined to the human body.

20

Though the lectures of Cuvier do not contain a Arrangecomplete system of physiology, the anatomical matter in ment of them is, however, so much blended with observations on Cuvier. the animal economy, that it will be of importance for the physiological student to be acquainted with his ar rangement.

The whole work is divided into 30 lectures: the first of which is occupied with preliminary observations on the animal economy, comprehending a general view of the functions of animal bodies; a general idea of the organs of which the animal body is composed; a view

of

of the principal differences exhibited by these organs, and of the relations which exist among those variations, together with a division of animals founded on their organization. The second lecture treats of the organs of motion in general; the third, fourth, fifth, and sixth lectures are merely anatomical, exhibiting a comparative view of these organs in the several classes of animals. The seventh lecture is strictly physiological, and treats of the organs of motion considered in the several actions of standing, walking, seizing and climbing, leaping, swimming, and flying.

The eighth, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, and fifteenth lectures, are occupied in considering the anatomy and physiology of the function of sensation. Of these, part of the ninth treats of the nervous system in general, and of its action; part of the twelfth gives the physiology of vision; part of the thirteenth, that of hearing; part of the fourteenth, that of touch; and part of the fifteenth, that of smell and taste.

The sixteenth, seventeenth, eighteenth, nineteenth, twentieth, and twenty-first lectures treat of the organs and phenomena of digestion, mastication, insalivation, and deglutition. The twenty-second lecture treats of what have been called the assistant chylopoietic viscera, namely, the liver, the pancreas, the spleen, and their offices. The twenty-fourth treats of the organs and phenomena of circulation in general; the twenty-sixth of those of respiration in general; the twenty-eighth of the organs of voice.

The twenty-ninth treats of the organs and phenomena of generation, and the thirtieth, of those of excretion, comprehending a general view, both of secretion and excretion.

Subjoined to Bichat's introduction to his Anatomie Generale, there is a tabular view of physiology, in which, after some preliminary outline of the general structure of the organs and of the phenomena of vitality, he divides the functions into classes, orders, and genera.

The first class consists of the functions that relate to the individual; the first order of which, comprising the functions of animal life, comprehends five genera, viz. sensations, cerebral functions, locomotion, voice, and nervous transmission, besides sleep. The second order of this class contains the functions of organic life, and comprehends eight genera, viz. digestion, respiration, circulation, exhalation, absorption, secretion, nutrition, and calorification.

The second class contains the functions that relate to the species in general, and is divided into three orders. The first of these, comprising the functions peculiar to the male, comprehends only one genus, viz. the production of the seminal fluid. The second comprises the functions peculiar to the female, and contains three genera, viz.menstruation, the production of milk, and of the female generative fluids. The third order comprises the functions that relate to the union of the two sexes, and the product of that union; and it comprehends also three genera, viz. generation, gestation, and delivery. Respecting the peculiar doctrines of this writer we shall speak hereafter.

There is still another mode of arranging the phenomena of living bodies, that deserves to be noticed, namely, that in which they are arranged according to the artificial systems of natural history. This mode of arVOL. XVI. Part II.

+

tion.

rangement, though of infinite advantage to the zoolo- Introducgist, by showing him at once the extent of his subject, and giving to his memory a power of recollection which it could not otherwise possess, is yet not such as the physiologist would wish to be observed. Zoological arrangements are useful chiefly as they facilitate the study of the manners, dispositions, and habits of different animals; and all that part of the outward economy which indicates something of the wisdom and design displayed by the Creator, in their structure and adaptation to the modes of life which they are intended to pursue; but they do not sufficiently illustrate the internal structure on which this outward economy depends, nor do they sufficiently explain the more secret functions, which being independent of the will of the creature, only dis. play the power and omniscience of him who made it. This will be readily conceived from considering the difference between zoology and physiology, as we have defined it. Zoology is chiefly led to examine the animal kingdom as it usually presents itself to the eye, including a great variety of objects; physiology examines only that part of the animal economy which is principally made known by anatomy and chemistry. Zoology has been accustomed to divide its kingdom into so many classes or orders of animals; physiology would naturally divide its economy into so many functions. Zoology has usually subdivided its classes by certain obvious external marks, as the teeth and claws; physiology would naturally subdivide its functions by the varieties of those organs which are destined to perform them, as the several kinds of lungs and stomachs. Zoology mentions the functions only in a cursory manner, as forming a part of the history of animals; physiology takes notice of animals, only when they are of use to illustrate the functions. To these differences we may add another; that physiology, in the extended sense which we have given it, goes beyond zoology in comprehending the economy of the vegetable creation. From this comparison it will be admitted, that things which are primary in a zoological method, will often be secondary in a physiological arrangement, and vice versa. This is very conspicuously the case in one of the grand divisions of Linnæus, viz. mammalia, where the important secretory organs of the milky fluid are noticed only like the colour of the hair, or the length of the tail, as a good outward mark of distinction, and likewise in the excellent table by D'Aubenton in his introductory view of natural history, in the Encyclopédie Methodique, in which the function of digestion is not even mentioned.

23

It is, however, extremely useful, both to the natural- Utility of ist and physiologist, that the arrangements of both sci- the appliences should be, as far as possible, adapted to each cation of physiologiother, by marking the relative importance of the seve-cal to zooral functions in the various classes of living beings. logical arThis has been very ably performed by Vicq d'Azyr, a rangement. modification of whose table has been given in the comparative part of our ANATOMY. See Vol. H. p. 280.

With respect to all physiological arrangements we may observe, that as the phenomena of living beings are so intimately dependent on each other, as to form the links of one continued chain, it is of little consequence which of the functions or phenomena we make the point from which we set out in our examination. But as the organs of sensation in most animals, and those of diges3 L

tion

24

25 Arrange

present article.

After giving a sketch of the progress of physiological ment of the discoveries and opinions, we shall divide the remaining part of the article into 16 chapters. In the first of these we shall treat of the characteristic marks, general phenomena, duration, and principle of life. In the second we shall consider the phenomena of sensation, the action of the nervous system, and the external senses of feeling, tasting, smelling, hearing, and sight. In the third and fourth chapters we shall treat of irritability, and the phenomena of motion. In the fifth we shall treat of digestion; in the sixth of absorption; in the seventh of circulation; in the eighth of respiration and voice; and in the ninth of nutrition, as completed by the successive performance of the four preceding functions. In the tenth chapter we shall treat of the phe

tion

nomena of secretion; and in the eleventh, of those of Introdecexcretion. In the twelfth we shall consider the various means by which living beings defend themselves from external injury, or the phenomena that attend the evolution and change of the iuteguments, to which function we shall give the name of integumation. In the thirteenth chapter we shall consider the transformations that take place in some tribes of living beings, especially insects and reptiles. In the fourteenth we shall briefly examine the phenomena of reproduction, and the hypotheses to which they have given birth. In the fifteenth we shall consider the nature of sleep, and the phenomena of dreams; and in the sixteenth we shall terminate our inquiries by a few observations on the nature and phenomena of death.

The following table is intended to exhibit an outline of the principal circumstances attending the phenomena of life, in the order in which we have enumerated them.

4 MOTION-Performed by

Fins.

The tail.

5. DIGESTION