152 LIFE AND DEATH. 



animal organism had nothing whatever to do but to 

 put this food into the tissues, or to arrange for it to 

 pass into the milk. But nature is not so wise and 

 economical as was supposed at the Academic des 

 Sciences. After a memorable debate, in which 

 Dumas, Boussingault, Payen, Liebig, Persoz, Chossat, 

 Milne-Edwards, and Flourens took part, and, later on, 

 Berthelot and Claude Bernard, it was agreed that 

 the animal does not grow fat from the fatty food 

 which is supplied it, and that it makes its own fat 

 just as the vegetable does, but in another manner. 

 In the same way sugar, the normal constituent sub- 

 stance necessary for the nutrition of animals and 

 plants, instead of being a vegetable product passing 

 by alimentation from the herbivorous animals and 

 thence to the carnivorous, is manufactured by the 

 animal itself. Generally speaking, immediate prin- 

 ciples have an equal claim to existence in the two 

 kingdoms. Both form and destroy the substances 

 indispensable to life. 



Here, then, one of the barriers between animal life 

 and vegetable life is overthrown and destroyed. 



Unity of Digestive Acts in Animals and Plants. 

 Similarly, another barrier falls if we show that 

 digestion, long considered the exclusive function of 

 animals, and, in particular, of the higher animals, is 

 in reality universal. 



Cuvier pointed out the absence of a digestive 

 apparatus as a very general and distinctive char- 

 acteristic of plants. But the absence of a digestive 

 apparatus does not necessarily imply the absence of 

 digestion. The essential act of digestion is indepen- 

 dent of the infinite variety of the organs, just as a 

 reaction is independent of the form of the vessel in 



