ORGANIC PROCESSES OF PLANTS AND ANIMALS. 1021 



accompanied by the same inorganic substances, in small quan- 

 tity, namely magnesia, phosphoric acid, lime, iron, alkalies and 

 sulphur. They evolve the same foetid odour when heated, and 

 give the same volatile products containing sulphur and phos- 

 phorus. 



Animals thus obtain the constituents of their bodies from 

 plants, if herbivorous, or from the bodies of other animals, if 

 carnivorous, and merely assimilate organic principles without 

 organising them. For the azotised vegetable principles take a 

 new form in the animal organism, without any change in their 

 chemical composition. The albumen, fibrin and casein of the 

 animal system also admit, from the identity of their ultimate 

 composition, of being readily converted one into the other, 

 according as each is required in the animal economy. Ani- 

 mal digestion comes thus to be deprived of much of its mystery. 

 M. Dumas has thus expressed himself, very lately, respecting 

 that process. 



" Digestion is a simple function of absorption. The soluble 

 matters pass into the blood, for the most part unaltered ; the 

 insoluble matters arrive in the chyle sufficiently divided to be 

 aspired by the orifices of the chyliferous vessels. Digestion has 

 evidently for an object to restore to the blood, a matter proper 

 to furnish for our respiration the ten or fifteen grammes of 

 carbon or the equivalent of hydrogen, which every individual 

 burns per hour, and also to provide the gramme of nitrogen, 

 which is exhaled every hour, in part by the lungs and skin, as 

 well as by the urine. Thus, amylaceous matters are converted 

 into gum and sugar ; the saccharine matters formed are absorbed. 

 The fat matters are divided, form an emulsion, and so pass into 

 the vessels, to form afterwards deposits, which the blood takes up 

 and burns, when they are required. The neutral azotised mat- 

 ters, the fibrin, albumen and casein, first dissolved, then pre- 

 cipitated, pass into the chyle highly divided or dissolved 

 anew. 



" An animal, therefore, receives and assimilates almost un- 

 touched, the neutral azotised matters which he finds ready formed 

 in the animals or plants upon which he lives ; he receives oily 

 substances which come from the same sources, and also amyla- 

 ceous and saccharine substances of the same origin. These 

 three orders of matters, of which the origin is* always traceable 



