190 THE VITAL FUNCTIONS. 



nourishment from materi-als which would other- 

 wise taint the whole system with their poison, 

 and soon prove destructive to life. 



It would appear that the first changes which 

 constitute digestion take place principally at 

 the cardiac end of the stomach, and that the 

 mass of food is gradually transferred towards 

 the pylorus, the process of digestion still con- 

 tinuing as it advances. In the Rabbit it has 

 been ascertained that food newly taken into 

 the stomach is always kept distinct from that 

 which was before contained in it, and which 

 has begun to undergo a change : for this pur- 

 pose the new food is introduced into the centre 

 of the mass already in the stomach ; so that 

 it may come in due time to be applied to the 

 coats of that organ, and be in its turn digested, 

 after the same change has been completed in 

 the latter.* 



As the flesh of animals has to undergo a less 

 considerable change than vegetable materials, 

 so we find the stomachs of all the purely carni- 

 vorous tribes consisting only of a membranous 

 bag, which is the simplest form assumed by 

 this organ. But in other cases, as we have 

 already seen, the stomach exhibits a division 

 into two compartments, by means of a slight 



* See Dr. Philip's Experimental Enquiry into the Laws of 

 the Vital Functions, 3d. edition, p. 122. 





