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.v.] OF ASSIMILATION AMONGST ANIMALS. 327 



globules is conveyed even into the finest capillary ramifications 

 of the circulatory system. There the globules meeting the waves 

 of carbonic acid, the expulsed residuum of the oxydation of 

 anatomical elements exchanges with this acid its oxygen, with 

 which it had only made a shifting combination. The oxygen 

 thus yielded goes, by endosmosis, to re- vivify the tissues, whilst 

 the carbonic acid, carried away in its turn by the globules, to 

 which it has imparted a sombre red tinge, is exchanged by them 

 for a fresh provision of oxygen, in the capillary vessels of the 

 special organs called respiratory. The respiration of the most 

 complex animals is summed up then in a series of very simple 

 acts : absorption by the red globules of aerian oxygen, cession 

 of this oxygen to the anatomical elements, in exchange for a 

 residuum of carbonic acid, finally the exchange of this carbonic 

 acid for a fresh supply of aerian oxygen. It is a ceaseless 

 circuit, which stops only with death. 



Almost the whole of the water contained in such large 

 proportion in the animal organism penetrates it from without, 

 either through the general surface of the body, as in inferior 

 organisms, or by that of the organs called digestive, as in the 

 complex animals. Nevertheless, it is probable that a considerable 

 quantity of water forms itself in the interior of the living 

 tissues themselves, by the complete oxydation of certain ternary 

 hydro-carbonated matters. The water besides conveys along 

 with it into the economy important quantities of calcareous, 

 alkaline, and ferruginous salts, and also a ceitain quantity of 

 air, which it holds in solution. Boussingault has stated that 

 the quantity of mineral substances imbibed each day at the 

 drinking trough by a milch-cow rises to 50 grammes. 



In weight, water forms the major part of every animal 

 organism, of every plasma, of every anatomical element. The 

 albuminoidal substances retain a notable quantity as constituent 

 water, another portion as water of imbibition. Water does 

 not seem to be directly decomposed amongst animals, and its 

 office is specially mechanical, but none the less important. It 



