PHYSIOLOGY. 



1-iVation of the term, a discourse on natu- 

 ral bodies : but it formerly denoted only 

 an internal reasoning 1 , which terminates in 

 speculation, or abstract contemplation of 

 its object ; namely, natural appearances, 

 their causes, &c. : but the usual accepta- 

 j tion of the word is very different in the 

 present state of science, as we shall see 

 by the following 1 article. 



PersioLOfiT is the science which treats 

 of the powers that actuate the compo- 

 nent parts of living animal bodies, and of 

 the functions which those bodies execute. 

 It presupposes, therefore, a knowledge 

 of the structure of the body, which is the 

 object of anatomy ; the latter may be 

 called the science of organization, while 

 physiology is the science of life. The 

 two subjects are so closely connected, 

 that they would be most advantageously 

 considered in connection with each other. 

 Hence the reader will find many physio- 

 logical considerations under the articles 

 ANATOMI and COMPARATIVE \WATOMT, 

 which indeed he should peruse as an in- 

 troduction to the present article. 



Genial View of the Functions exercised by 

 the animal Body. 



The term life denotes one of those ge- 

 neral and obscure notions produced in 

 our minds by certain -series of phenome- 

 na, which we have observed to succeed 

 each other in a constant order, and to be 

 connected together by mutual relations. 

 Being ignorant of the bond of union 

 which connects these, although we are 

 convinced of its existence, we have de- 

 signated the assemblage of phenomena 

 by a name which is often regarded as the 

 sign of a peculiar principle ; although it 

 should indicate nothing more than the 

 collection of appearances, which have 

 given rise to its formation. Thus, as our 

 own bodies, and several others, which 

 resemble them more or less strongly in 

 form and structure, appear to resist for a 

 certain time the laws which govern in- 

 animate matter, and even to act on sur- 

 rounding objects in a manner quite con- 

 trary to these laws, we employ the ex- 

 pressions of life and vital power, to de- 

 signate these at least apparent exceptions 

 to general rules. Our only method of 

 fixing the meaning of these words is, to 

 determine exactly in what these excep- 

 tions consist. With this object, let us 

 consider the bodies alluded to in their 

 active and passive relations to the rest of 

 nature. Let us contemplate, for instance, 

 the body of a female in the vigour of 

 youth and beauty; those rounded and 



voluptuous forms; those graceful anxl 

 easy motions; those cheeks glowing with 

 the roses of pleasure; those eyes spark- 

 ling with the inspirations of genius, or 

 fired by the warmth of love; that physi- 

 ognomy enlivened by the sallies of wit, 

 or animated by the fire of the passions ; 

 all unite to form a truly enchanting ob- 

 ject. A single moment is sufficient to 

 destroy this pleasing illusion : sensation 

 and motion often cease on a sudden, with? 

 out any apparent pre-existing- cause ; the 

 muscles, losing their plumpness, shrink, 

 and expose the angular projections of the 

 bones; the lustre of the eyes is gone, the 

 cheeks and lips grow livid. These are 

 only the prelude to still more unpleasant 

 changes : the flesh turns successively to 

 blue, green, and black; it imbibes the 

 moisture of the atmosphere, and, while 

 one part is evaporated in pestilential ema- 

 nations, the other melts into a putrid 

 sanies, which also is speedily dissipated. 

 In short, after a few days, nothing re- 

 mains but a few earthy, or saline princi- 

 ples; the other elements having been 

 dispersed in the air, or waters, to form 

 new combinations. 



This separation is the natural effect of 

 the action of air, moisture, and heat, that 

 is, of all the surrounding external agents, 

 on the dead body ; and it. arises from the 

 elective attractions which these agents 

 possess for the materials of the body. 

 Yet it was equally surrounded by them 

 during life : their affinities for its com- 

 ponent parts were the same ; and the 

 latter would have yielded in the same 

 manner, if they had not been held to- 

 gether by a superior power, the influence 

 of which continues to operate until the 

 moment of death. 



This resistance then, of the laws which 

 act on dead matter, is one of the particu- 

 lar ideas entering into the general notion 

 of life, which seems, in a more especial 

 manner, to constitute its essence ; for 

 without it life cannot be conceived to 

 exist, and it continues uninterruptedly 

 until the moment of death. 



Almost endless disputes have arisen 

 among physiologistsconcerningthe essen- 

 tial nature of this vital principle. Vitality 

 is one of those attributes which can be 

 more easily discerned and recognized 

 when present in any object, than accu- 

 rately defined. Definition indeed would 

 be more likely to confuse than to illustrate 

 it. It is manifested most incontestibly 

 by certain effects, referable to peculiar 

 powers, which are jusUy called living or 

 vital, because the actions of the living- 

 body are so far depending on these pow- 



