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stomach, which does not exceed that of the rest of the body, (32 degrees 

 of Reaumur's scale) would be insufficient. Cold-blooded animals digest 

 equally with the warm-blooded, and, as Vanhelmont observes, febrile 

 heat impairs, instead of increasing the powers of digestion. In the lan- 

 guage of the ancients, concoction means the alteration, the maturation, 

 the animalizationof alimentary substances, assimilated to our nature, by 

 the changes which they undergo in the cavity of the stomach. It is, how- 

 ever, a verified fact, that the natural heat of the stomach promotes and 

 facilitates those changes. The experiments of Spallanzani on artificial 

 digestion, show, that the gastric juice is not of more efficacy than plain 

 water, in softening and dissolving alimentary substances, when the heat 

 is below seven degrees (of Reaumur's scale;) that its activity, on the con- 

 trary, is greatly increased when the heat is ten, twenty, thirty, or forty 

 degrees above the freezing point. The digestion in the cold-blooded ani- 

 mals is, besides, slower than in the hot-blooded. 



XVI. The abettors of the theory of fermentation admit that the food 

 taken into the stomach undergoes an inward and spontaneous motion, in 

 virtue of which it forms new combinations; and as the process of fer- 

 mentation is promoted, by adding, to the substance th-at is undergoing 

 that change, a certain quantity of the same that has already undergone 

 the process ; some have supposed that there continually exists in the 

 stomach a leaven, formed, according to Vanhelmont, by a subtle acid, 

 and consisting, in the opinion of others, of a small quantity of the food 

 that remains from the former digestion. But, independently of the cir- 

 cumstance that the stomach empties itself completely, and presents no 

 appearance of leaven, when examined a few hours after digestion, sub- 

 stances undergoing fermentation require to be kept perfectly at rest, 

 whereas the food is exposed to the oscillatory circulations and to the pe- 

 ristaltic contractions of the stomach, and this viscus is shaken by the 

 pulsations of the neighbouring arteries; it is besides kept in continual 

 motion by the act of respiration. In fermentation gases are either ab- 

 sorbed or extricated, neither of which circumstances takes place when 

 the stomach is not out of order. 



It should, however, be stated, in support of the opinion that accounts 

 for digestion on the principle of fermentation, that we can derive nourish- 

 ment, only from substances capable of undergoing fermentation, and that 

 the substances which have undergone the panaryand saccharine fermen- 

 tation are more easily digested, and in less time. This imperceptible 

 fermentation, if it really take place, must bear a greater analogy to these 

 two last processes, to those which are called vinous and acetous fer- 

 mentation: but no one can differ from it more than the putrid fermen- 

 tation. 



XVII. There have been physiologists, however, from the time ofPlis- 

 tonicus, the disciple of Pruxagoras, who maintain, that digestion is, in 

 fact, the consequence of putrefaction. But, not only is ammonia not dis- 

 engaged during that process, but our digestive organs have the power, 

 as will be seen presently, of retarding, or of suspending, the putrefaction 

 of the substances which are submitted to their action. In serpents, 

 which in consequence of the great power of dilatation of the oesophagus, 

 and from the power of holding asunder their jaws, both of which are 

 moveable nearly in an equal degree, frequently swallow larger animals 

 than themselves, and take several days to digest them; that part of the 

 animal which is exposed to the action of the stomach, is observed to be 



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