66 



exist in the foetus, which neither breathes, nor digests', c. Nothing in 

 the animal oeconomy, said Galen, is ruled by invariable laws, or can be 

 subject to the same accurate results and calculations, as an inanimate ma- 

 chine, (Nilestin corpore viventi filane sincerum. GALEN.) Thus, respiration, 

 which connects the external and assimilating function, furnishes the blood 

 with the principle which is to keep up the action of the brain, and to ex- 

 cite musculai contractions. On the other hand, the motion of the mus- 

 cles is of use in the distribution of the humours, and concurs in the phe- 

 nomena of assimilation. The brain, by means of the eighth part of nerves, 

 holds influence over the stomach. The sensations of taste and smell seem 

 to preside, in an especial manner, over the choice of food and of air, and 

 to belong rather to the digestive and respiratory functions, than to those 

 of the intellect, or of thought. 



We have seen in this kind of general introduction of the study of phy- 

 siology, what idea is to be formed of that science as well as of life, the 

 study of which is its object ; into how many classes the beings in nature 

 may be divided, and into how many elements they are resolvable; what 

 differences exist, between inorganized, organized and living bodies, 

 between plants and animals; how life is complicated, modified, and ex- 

 tended, in the immense series of beings which are endowed with it, from 

 the plant to man ; anc4 in further particularizing the object under our 

 consideration, we have examined, what are the organs which, by their 

 union, form the human machine ; what powers govern the exercise of 

 their functions : then, we have laid down the fundamental laws of sensi- 

 bility and contractility, we have spoken of sympathies and habits, of the 

 internal nervous apparatus, which unites, collects, and systematizes the 

 organs of the assimilating function ; we have endeavoured to determine 

 from facts, the existence of the cause which subjects living beings to a 

 set of laws very different from those which inorganic matter obeys. The 

 knowledge of these laws is the light which is to guide us in the applica- 

 tion to physiology of the accessory sciences. Finally, in the arrangement 

 of the objects which this science considers, I have adopted a more sim- 

 ple and natural division than any hitherto employed. 



I shall close this preliminary discourse, by saying a few words on the 

 order adopted in the distribution of the chapters. I might have begun by 

 a view of the external functions, as well as those of assimilation or nutri- 

 tion, of sensation, or of digestion. I have given preference to the func- 

 tions of assimilation, because of all others, they are the most essential to 

 existence, and their exercise is never interrupted, from the instant in 

 which the embryo begins to live, till death. In beginning, with an ac- 

 count of them we imitate nature therefore, who imparts to man this mode 

 of existence, before she has connected him with outward objects, and who 

 does not deprive him of it, until the organs of sense, of motion, and of 

 the voice, have completely censed to act. 



As to the course which has been followed in the arrangement of the 

 functions that belong to the same order, or which concur in the same end, 

 it was too well laid down by nature, to .allow us to depart from it. I have* 

 thought it right that the consideration of the voice should immediately 

 precede that of generation, in order that the arrangement might, at a 

 glance, show the connexion which exists between their phenomena. 

 Several animals us.e their voice only during the season of love ; the birds 

 which sing at all times have, during that period, a more powerful and so- 

 norous voice. When man becomes capable of reproduction, his vocal 



