68 



IMMEDIATE PRINCIPLES OF THE TISSUES. 



N 



Fig. 36. 



composed into these and similar substances in the living body, and 

 thus expelled in the urine. 



2. Creatinine. (C 8 H 7 N 3 O 2 .) 



The crystals of creatinine are shown by Fig. 36. gj It is found 

 only in the muscles and the urine, and always in company with 



creatine. The liquor amnii also 

 probably contains it. (Scherer.) In 

 the muscles it is far less abun- 

 dant than creatine ; in the urine 

 it is far more so. 



Origin. Creatinine is pretty 

 certainly produced in the organ- 

 ism from creatine, being one de- 

 gree lower than the latter in the 

 descending metamorphosis of the 

 tissues. It differs from creatine 

 merely in containing two equi- 

 valents less of water, or is crea- 



Creatmine crystallized from hot water. tine minUS 2(HO). 



3. Urea. (C 2 H 4 N 2 2 .) 



Urea is the most highly nitrogenized compound in the body. It 



crystallizes, if slowly, in flat, 

 colorless, four-sided prisms (Fig. 

 37); if rapidly, in white, silky, 

 glistening needles. It is found 

 in the urine, the blood, and the 

 vitreous and aqueous humors of 

 the eye. It exists in combina- 

 tion with common salt (i. e. as 

 chloro-sodate of urea), in the 

 blood and the vitreous humor, 

 and partly so, also, in the urine. 

 (Robin and Verdeil) Urea does 

 not exist in the muscular juice. 

 (G-rohe) It sometimes exists in 



Urea slowly crystallized from aqueous solution. ^^ ( ^^ ^ y ^ often in 



dropsical transudations. In Bright's disease it is found in all the 

 serous fluids, and sometimes in the saliva. 



Fig. 37. 



