154 LIFE AND DEATH. 



The same conclusions are true for another class 

 of substances, the sugars. They may be a food taken 

 from without, or a reserve deposited in the tissues. 

 The animal takes from without, in fruits for instance, 

 the ordinary sugar which pleases its taste. Beetroot, 

 when flowering and fructifying, draws this substance 

 from its roots in which stores have been amassed. 

 The sugar cane when running to seed takes the 

 sugar from the stores which it possesses in its cane. 

 Brewer's yeast, the saccharomyces cerevisice, the agent 

 of alcoholic fermentation, finds this same substance in 

 the sugary juices favourable to its development. 



In the same way, identically fatty substances, 

 either in the form of food or of reserve-stuff, serve 

 for nutrition to animals and vegetables ; and that is 

 again true of the substances of the fourth class, 

 albuminoids, identical in the two kingdoms, foods or 

 reserve-stuff, equally utilizable in both after digestion. 



Identity of the Digestive Agents and Mechanisms in 

 Plants and Animals. — Now, the results of contem- 

 porary research have been to establish a surprising 

 resemblance in the modifications experienced by these 

 foods, or reserve stuffs, in animals and plants; and 

 even resemblances in the agents which realize them, 

 and in the mechanisms by which they are performed. 

 There is a real unity. The flour accumulated in the 

 tuber of the potato is liquefied and digested on the 

 appearance of the buds or of the flower, just as the 

 starch of the liver or the alimentary flour is digested 

 by the animal. The fatty matter which is stored up 

 in the oleaginous grain is digested at the moment of 

 germination, just as the fat during a meal is digested 

 in the animal's intestine. As the beetroot begins to 

 run to seed, the root gives up part of its store of 



