174 BIOLOGY. [BOOK IT. 



aquatic mediums, the flora is little diversified. It is almost 

 entirely composed of sea-weeds, plants of very simple structure, 

 of a soft consistency, and of a chemical composition everywhere 

 almost identical. The digestive apparatus of the marine 

 herbivora has then only a uniform work, of relative simplicity, 

 to accomplish, while, on the contrary, the aquatic fauna being 

 extremely varied, the alimentation which it furnishes resembles 

 it ; and consequently necessitates a digestive system adapted to 

 render absorbable, aliments very dissimilar from each other. 



Alimentary variety seems even to be a necessity for certain 

 herbivora, and Magendie has seen rabbits only live fifteen days, 

 that is die of inanition, when compelled to live solely upon one 

 of the vegetals which constituted their ordinary alimentation 

 (carrots, cabbages, barley, &c.). 



Besides, we must guard against attaching an absolute value to 

 the denominations herbivora and carnivora. As M. Schiff points 

 out in his excellent Traite de la Digestion, 1 there is no essential 

 difference between the gastric juice of herbivora and that of] 

 carnivora. Both disaggregate the vegetal or animal aliments, 

 both dissolve the albuminoidal substances, and everything that 

 is soluble in acidulated water. The herbivorous gastric juice is 

 only a little less active, and, though of equal weight, it digests 

 fewer albuminoidal matters than the carnivorous gastric juice. 

 But, by causing a rabbit to absorb, either through the blood or 

 through the stomach, various soluble substances (peptogens) 

 which have the property of rendering the gastric juice more 

 active, we succeed in making the stomach of a rabbit functionate 

 like the stomach of a dog or a cat. At all events the peptones 

 prepared at the expense of the albumine by the stomach of a 

 herbivorous animal are directly assimilable by the tissues of a 

 carnivorous animal, and if we inject them either into its stomach, 

 or direct into its veins, they are perfectly absorbed, and we do 

 not find them again in the urines, as happens with every non- 

 assimilated substance. 



1 T. II., pp. 183, 184.^ 



