HOW TIIK ANIMAL LIVES 237 



parts of the body, is n siniple straw-colored liijuid i-uiisisling 

 of Hurplua nutritive iiiatttT which hns not been recjuired by 

 tht» needs of the part, and is l)i'iiip returned to the blood. 

 In this lymph we tiud an important source of supply of the 

 white blootl jjlobuk-s, which are being constantly used up ; 

 ami thus deranf^cments in the lymph vessels and f^lands injuri- 

 ously affect the blood, and through it the entire animal system. 

 AOOh. The admirable adaptation of means to end is trace- 

 able in the sucoessive changes of these food products. The 

 nitrogenous constituents in the food, which are not fitted for 

 absorption, are transformed into the peptones, which are spe- 

 cially adapted for rapid absorption. Then the peptones, which 

 are not fitted for nutrition, but are really poisonous, are changed 

 in the liver, so as to render them harmless aiul fitt«'d for the 

 varied uses of the body, or for elimination. Other food princi- 

 ples aro turned into su;,'ar, and sonu' poisonous fermentation 

 pro<luct9 are rendered harmless through the action of the liver. 

 This interdependence of different functions upon each ucher — 

 mastication, insativation, digestion, absorption, transformations 

 in the liver, the formation of normal bluod elements, assimi- 

 lation ond secretion — furnishes an indication of what goes on 

 throughout the whole animal body, the perfection of one process 

 being essential to that of others, and the derangement of one 

 causing disorder of the others. The nervous system, which is 

 concerned in currying on all functions, from those of simple 

 nutrition of a tissue or of secretion by a gland up to such mental 

 processes aa the animal is endowed with, is dependent on the 

 blood for its own functional activity. Changes in the blood 

 CDtail change in tho capacity for nervous work ; so that disorder 

 of one distant organ, acting by influencing the nervous system, 

 directly through tho nerves or indirectly through the blood, 

 may bring about derangements of the most varied kind in the 

 different organs subject to ner%'ous influence. The great func- 

 tion of the lungs is the elimination of carbon dioxid from the 

 blood ard tissues and tho introduction of oxygen, which, being 

 corrted into all parts by tho red globules, assists in nearly 

 "v«.'-v ••)i.<\nge which takes place in any organ. But if the lung^ 



