42 



might be imagined, on the very complicated steps of which a ballet r* 

 composed. 



Morbid sensibility, is equally under the influence of habit. I have al- 

 ways observed, that discharges from the urethra become less painful from 

 their frequency. There is nothing down to disease itself, that is uotmade 

 lighter by habit, as has been well observed by Hippocrates. 



It remains then demonstrated, even as a general thesis, that habit, or 

 the frequent repetition of the same acts, while it regularly reduces physi- 

 cal sensibility, improves intelligence, and gives facility and promptness to 

 all the motions that are under the direction of the will. 



IX. OF THE VITAL PRINCIPLE*. 



The words -vital principle, vital force, See. do not express a being exist- 

 ing by itself, and independent of the actions by which it is manifested: 

 it must be used only as an abridged formula, which serves to mark the 

 total of the powers that animate living bodies, and distinguish them 

 from inert matter. So that, whenever, in the course of this section, I 

 shall use these terms, or any equivalent, it is to be taken as if I had said, 

 the aggregate of the properties and laws that regulate the animal cecono- 

 my. This explanation is become indispensable, now that several wri- 

 ters, realizing a mere abstraction, have spoken of the vital principle, 

 as of something very distinct from the body, as of a being altpgether se- 

 parable, which they have invested with feeling, and thought, and even 

 deliberate intentions. 



From the remotest antiquity, the many and striking differences of liv- 

 ing, and inorganic bodies, have led some philosophers to conceive in the 

 former, a principle of particular actions, a force which maintains the har- 

 mony of their functions, and directs them all to a common end, the pre- 

 servation of individuals and of the species. This simple and luminous 

 doctrine, has remained, even to our own days, only modified in its pas- 

 sage through many years : and, no one now disputes the existence of a 

 principle of life, which subjects the beings, that enjoy it, to a system of 

 laws different from those which inanimate beings obey ; a force which 

 might be characterized, as withdrawing the bodies it animates, from the 

 absolute dominion of chemical affinities, which would else, from the 

 multiplicity of their elements, oct on them with great power ; and as 

 maintaining them in a nearly equal temperature, whatever may be that 

 of the atmosphere. Its essence is not in preserving the aggregation of 

 constituent molecules, but in drawing to it other molecules, which, by 

 assimilation to the organs it pervades, replace those that are carried off 

 in daily waste, and serve for their nourishment and growth. 



All the phenomena that are to be observed in the living human body, 

 might be brought as proofs of the principle which animates it. The 

 actions of the digestive organs on its food ; the absorption, by the chy- 

 lous vessels, of its nutritious parts; the circulation of these nutritious 

 juices through the sanguineous system ; the changes they undergo in 

 their passage throughnhe lungs, and the secretary glands; the impressi- 

 bility by outward objects ; the power of approaching or avoiding them; 

 in a word, all the functions that are carried on throughout the animal 



See APPENDIX, Note A. 



