PHYSIOLOGY. 



any part of a living body arises from the 

 whole ; while, in dead matter, each par- 

 ticle has it within itself. 



When this nature of life was once 

 clearly recognised by the most constant 

 of its" effects, physiologists naturally at- 

 tempted to discover its origin, and the 

 mode of its communication to bodies 

 which it animates. They looked at them 

 in their earliest state, approaching as 

 nearly as possible to the instant of their 

 formation ; but they could only discover 

 them completely formed, and already 

 possessing that circulatory motion, of 

 which they were investigating the first 

 cause. However delicate the parts of a 

 foetus, or a vegetable, in the first moments 

 that we can perceive them, they still pos- 

 sess life, and have within themselves the 

 germ of all the phenomena which this life 

 will develope in the sequel. These ob- 

 servations having been repeated in every 

 class of living bodies, have led to the 

 general conclusion, that there is none 

 which has not formerly constituted part 

 of a body like itself, from which it has 

 been detached; all have participated of 

 the life of another body, before the vital 

 motions were carried on independently 

 in themselves ; and it is, indeed, through 

 the means of the vital powers, inherent 

 in the bodies of which they formed part, 

 that they have been so far developed as to 

 become susceptible of an isolated life. 

 For although copulation is necessary in 

 the act of reproduction in several species, 

 it is by no means an essential circum- 

 stance, and does not, therefore, change 

 the nature of generation. In reality, then, 

 the peculiar powers of living bodies have 

 their origin in those of the parents; this 

 is the source of the vital impulse, and, 

 consequently, it follows, that life is only 

 produced from life, and that no other ex- 

 ists, except what has been transmitted 

 from living bodies to living bodies, in an 

 uninterrupted succession. 



Since we cannot go back to the first 

 origin of living bodies, our only resource 

 in investigating the true nature of the 

 powers which animate them consists in 

 examining their structure, and tracing the 

 union of their elements, Our knowledge 

 of these points is too imperfect for us to 

 draw all the necessary inferences. The 

 minute branches of vessels and nerves, 

 and the intimate structure of the organs 

 in general, elude our imperfect means of 

 research: our analysis of fluids is also 

 very incomplete, and there are, probably, 

 several of which we have no means at all 

 of subjecting to examination. Yet, though 

 our knowledge of organization be not 



sufficient to enable us to explain all the 

 facts presented to our observation by 

 living bodies, we may, by means of it, re- 

 cognise them, even in an inactive state, 

 and trace their remains after death. No 

 inanimate matter has that fibrous and 

 cellular texture, nor that multiplicity of 

 volatile elements which form the charac- 

 ters of living bodies, whether alive or 

 dead. Thus, while inorganic solids are 

 only composed of many-sided particles, 

 attracting each other by their surfaces, 

 and receding only for the purpose ot se- 

 parating ; while they are resolved into a 

 very limited number of elementary sub- 

 stances, and are formed merely by the 

 combination of these elements, and the 

 aggregation of these particles ; while they 

 grow only by the juxta-position of new 

 particles, which are deposited exteriorly 

 to those already existing, and are de- 

 stroyed only by the mechanical separa- 

 tion of their parts, or the decomposing 

 agency of chemical means; organiz-ed 

 bodies, made up of fibres and lamina?, 

 whose intervals are filled by fluids, are 

 resolved almost entirely into volatile ele- 

 ments, grow on bodies similar to them- 

 selves, and separate from these only when 

 they are sufficiently developed to act by 

 their own powers ; constantly assimilate 

 foreign matters to themselves, and, inter- 

 posing these between their own particles, 

 grow by the operation of an internal pow- 

 er, and perish at last by this interior prin- 

 ciple ; indeed, by the very effect of their 

 life. 



An origin by generation, a growth by 

 nutrition, and a termination by death, are 

 the general characters common to all or- 

 ganised bodies ; and if several of such 

 bodies possess these functions only, and 

 such as immediately depend on them, 

 awd have only the organs required for 

 their performance, there are many others 

 exercising particular functions which re- 

 quire appropriate organs, and also modi- 

 fy the general functions and their organs. 



Of all the less general powers, which 

 presuppose organization, but which do 

 not seem to be necessary results of struc- 

 ture, those of sensation and voluntary 

 motion are the most remarkable, and ex- 

 ert the greatest influence over the other 

 functions. We are conscious of the exist- 

 ence of these powers in ourselves, and 

 we attribute them, by an analogical mode 

 of reasoning, to many other beings, which 

 we therefore name animated beings or 

 animals. They seem to be necessarily 

 connected together ; tor the idea of vo- 

 luntary motion contains in itself that of 



