396 



THE URINE. 



CRYSTALS OP AMMO>- IO-MAGNESIA w 

 PHOSPHATE, deposited from healthy uriue, 

 during the alkaline fermentation. 



133 - increase, so that after seven or 



eight days they may become 

 visible to the naked eye. 



As the decomposition of the 

 urine continues, the ammonium 

 carbonate which is produced, 

 after saturating all the other 

 ingredients with which it is ca- 

 pable of entering into combina- 

 tion, begins to be given off in a 

 free form. The urine then ac- 

 quires an ammoniacalodor; and 

 a piece of moistened test-paper, 

 held a little above the surface, 

 will have its color turned by 

 the alkaline gas escaping from 

 the fluid. This is the source 

 of the ammoniacal vapor given 



off wherever urine is allowed to remain and decompose. It continues 



until all the urea has been decomposed. 



Renovation of the Body in the Nutritive Process. 



As the materials of nutrition are constantly introduced with the food, 

 while, on the other hand, the products of excretion are removed from 

 the body and discharged externally by the breath, the perspiration, the 

 urine, and the feces, an incessant renewal takes place in the ingredients 

 of which the animal system is composed. During the early periods of 

 growth and development, the quantity of material introduced is greater 

 than that discharged, and the body consequently increases in weight 

 and size. In wasting diseases and in advanced age, the loss of sub- 

 stance by excretion exceeds the gain by nutrition, and the weight of 

 the body is therefore diminished. But during health, in adult life, the 

 two processes are equal; and, with certain temporary fluctuations 

 which counterbalance each other, the weight of the body remains the 

 same. 



The total quantity of material, introduced and discharged within a 

 given time, forms, accordingly, a measure of the rapidity with which the 

 internal changes of nutrition and metamorphosis go on in the animal 

 system. It is not possible to indicate this quantity in either case with 

 absolute accuracy; but the observations which have been made in this 

 direction are sufficiently definite to show, in a general way, the average 

 results of the two corresponding actions of waste and supply. The 

 following table gives, approximately, the daily quantity of material 

 absorbed and discharged in a healthy adult, the weight of the body 

 remaining sensibly unaltered : 





