RENOVATION BY NUTRITIVE PROCESS. St33 



ammoniacal odor ; and a piece of moistened test paper, held a little 

 above its surface, will have its color immediately turned by the 

 alkaline gas escaping from the fluid. This is the source of the 

 ammoniacal vapor which is so freely given off from stables and from 

 dung heaps, or wherever urine is allowed to remain and decompose. 

 This process continues until all the urea has been destroyed, and 

 until the products of its decomposition have either united with 

 other substances, or have finally escaped in a gaseous form. 



RENOVATION OF THE BODY BY THE NUTRITIVE PROCESS. We 

 can now estimate, from the foregoing details, the entire quantity of 

 material assimilated and decomposed by the living body. For we 

 have already seen how much food is taken into the alimentary canal 

 and absorbed by the blood after digestion, and how much oxygen 

 is appropriated from the atmosphere in the process of respiration. 

 "We have also learned the amount of carbonic acid evolved with the 

 breath, and that of the various excretory substances discharged from 

 the body. The following table shows the absolute quantity of these 

 different ingredients of the ingesta and egesta, compiled from the 

 results of direct experiment which have already been given in the 

 foregoing pages. 



ABSORBED DURING 24 HOURS. DISCHARGED DURING 24 HOURS. 



Oxygen . . . 1.019 Ibs. Carbonic acid . . 1.535 Ibs. 



Water . . . 4.735 " Aqueous vapor . 1.155 " 



Albuminous matter . .396 " Perspiration . . 1.930 " 



Starch . . . .660 " Water of the urine . 2.020 " 



Fat 220 " Urea and salts . .110 " 



Salts .040 " Feces . . . .320 " 



7.070 7.070 



Rather more than seven pounds, therefore, are absorbed and dis- 

 charged daily by the healthy adult human subject ; and, for a man 

 having the average weight of 140 pounds, a quantity of material, 

 equal to the weight of the entire body, thus passes through the 

 system in the course of twenty days. 



It is evident, also, that this is not a simple phenomenon of the 

 passage, or filtration, of foreign substances through the animal 

 frame. The materials which are absorbed actually combine with 

 the tissues, and form a part of their substance ; and it is only after 

 undergoing subsequent decomposition, that they finally make their 

 appearance in the excretions. None of the solid ingredients of the 

 food are discharged under their own form in the urine, viz., as 



