HOW THE ANIMAL LIVES 237 



parts of the body, is a simple straw-colored liquid consisting 

 of surplus nutritive matter which has not been required by 

 the needs of the part, and is being returned to the blood. 

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

 white blood globules, which are being constantly used up ; 

 and thus derangements in the lymph vessels and glands injuri- 

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

 4096. The admirable adaptation of means to end is trace- 

 able in the successive changes of these food product*. 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 and fitted for the 

 varied uses of the bod} 7 , or for elimination. Other food princi- 

 ples are turned into sugar, and some poisonous fermentation 

 products are rendered harmless through the action of the liver. 

 This interdependence of different functions upon each other 

 mastication, insalivation, digestion, absorption, transformations 

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

 lation and secretion furnishes an indication of what goes on 

 throughout the whole animal bod}', 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 carrying on all functions, from those of simple 

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

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

 blood for its own functional activity. Changes in the blood 

 entail change in the capacity for nervous work ; so that disorder 

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

 directly through the nerves or indirectly through the blood, 

 may bring about derangements of the most varied kind in the 

 different organs subject to nervous influence. The great func- 

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

 blood and tissues and the introduction of oxygen, which, being 

 carried into all parts by the red globules, assists in nearly 

 every change which takes place in any organ. But if the lungs 



