92 



CHEMICAL COMPOSITION OF THE BODY. 



retrogressive metamorphosis of the albuminous compounds in man. Its ex- 

 treme solubility, and the facility with which as a "crystalloid" it permeates 



FIG. 53. 



Urea. 



Hydrochlorate of guauin. 



animal membranes, permit it to be readily discharged by the urine, of which 

 it is the most important constituent. 



GUANIN, C 3 H 5 N.O. An amorphous, yellowish-white substance, nearly 

 insoluble in alcohol, ether, and water; easily soluble in acids and alkalies. 

 By oxidation with potassium permanganate, guauin is converted into urea, 

 oxalic acid, and oxyguanin. It constitutes the greater part of the excre- 

 ments of spiders, but has also been found in the pancreas and liver, and, as 

 its name imports, in guano. It forms crystalline combinations with various 

 acids, one of which is represented in the adjoining woodcut, and also with 

 lime and soda. 



HYPOXANTHIN (Sarkin), C-H 4 1S" 4 O, appears in the form of- colorless, mi- 

 croscopic, crystalline granules, of no recognizable shape, which are soluble 

 in 300 parts of cold and 76 of hot water, and readily dissolve in acids and 

 alkalies. By nitric acid it is converted into xanthin. It has been found 



FIG. 54. 



FIG. 55. 



Nitrate of hypoxanthin. 



Hydrochlorate of hypoxanthin. 



Fie. -' 



in the blood and urine, especially of leukrcmic patients, in the juice of flesh, in 

 the liver, spleen, thymus, thyroid, kidney, and brain. It unites with acids to 

 form salts, which, as in the accompanying woodcut, form well-defined crystals-. 

 XANTHIN, C 5 H 4 N 4 O r This substance, which was first found in certain 

 rare urinary calculi, is amorphous, and presents both in its chemical consti- 

 tution and in the places where it is found, the closest 

 analogy to hypoxanthin. It is soluble in 1400 parts 

 of boiling and 14,500 parts of cold water. It is solu- 

 ble in ammonia, from which solution, by slow evapor- 

 ation, it is again deposited in confused crystalline 

 scales. It combines with acids, and then presents 

 characteristic crystalline forms. The very intimate 

 connection which exists between the three last-men- 

 - of xanthin. tinned substances and uric acid, C 3 H 4 N 4 O.j, is deserving 



