URINE OF COLD-BLOODED ANIMALS. 129 



merable globules of the urate of ammonia, resembling, in all respects, the solid 

 portion of the urine of birds. Epithelial cells and fibrinous casts of the urinary 

 tubes, were also found. 



The following are the results of the microscopical and chemical examination of 

 the urine of this snake : — 



Urate of ammonia, in great abundance. Phosphate of soda. 



Phosphate of lime. Chloride of sodium. 



" of ammonia. Epithelial cells. 



" of magnesia. Fibrinous casts of urinary tubes. 



We were unable to detect the presence of urea. .We have, however, found this 

 substance in small amount in the urine of other serpents. 



The urine of the Black Viper (Heterodoa niger), Hognose Viper (Heterodon pla- 

 tyrliinos), Indigo Snake (Coluber couperi), Corn Snake (Coluber guttatus), Chicken 

 Snake (Coluber quadrioitlatus), Rattlesnake (Crolulus adamanteus), and others 

 yielded similar results upon a qualitative examination. 



In the kidneys of the Indigo Snake (Coluber couperi), several pyriform calculi 

 were found imbedded in their substances, extending from their anterior surfaces to 

 the uterus. These calculi were found to consist, in large measure, of the oxalate 

 of lime. Other substances were also present — as urate of ammonia and the phos- 

 phates of lime, ammonia, and magnesia. 



The amount of urine excreted by the kidnej-s of Ophidians, during starvation, is 

 exceedingly small. I have kept them, without food or drink, for several weeks, 

 and the amount excreted during this time, often did not amount to more than 20 

 or 50 grains. 



A male Alligator (Alligator Mississippiensis), which weighed 76,507 grains, was 

 starved and deprived of water for eighteen days, and during that time it discharged 

 its urine but once, in quantity about two fluidounces. This consisted, as in Ophi- 

 dians and Birds, of a fluid and a solid, chalk-like portion, composed of minute globules 

 of the urate of ammonia. 



We shall next consider the urine of Chelonians. In these animals the bladder 

 is large, and the urine resembles, in many respects, that of the Mammalia. The 

 following table represents the specific gravities of the urine in its normal condition, 

 and during starvation and a change of diet : — 



17 



