346 EXCRETION 



water and is even more soluble in boiling water. It is slightly soluble 

 in ether and is dissolved by one hundred parts of alcohol. This sub- 

 stance is one of the strongest of the organic bases, readily forming 

 crystalline combinations with a number of acids. According to Thudi- 

 chum, creatin is the original excrementitious substance produced in the 

 muscular substance, and creatinin is formed in the blood by a trans- 

 formation of a portion of the creatin, somewhere between the muscles 

 and the kidneys ; " for, in the muscle, creatin has by far the preponder- 

 ance over creatinin ; in the urine, creatinin over creatin." The fact that 

 creatin has been found in the brain would lead to the supposition that 

 it is also one of the products of katabolism of nervous tissue. 



The average daily excretion of creatin and creatinin has been esti- 

 mated at about 11.5 grains (0.745 gram). Of this, Thudichum estimated 

 that 4.5 grains (0.292 gram) consisted of creatin, and 7 grains (0.453 

 gram) of creatinin. 



Calcium Oxalate. Calcium oxalate (oxalic acid,C 2 H 2 O 4 ) is not con- 

 stantly present in normal human urine, although it may exist in certain 

 quantity without indicating any pathological condition. It is exceed- 

 ingly insoluble, and the appearance of its crystals, which commonly are 

 in the form of small regular octahedra, is quite characteristic. A small 

 quantity may be retained in solution by the acid sodium phosphate in 

 the urine. Calcium oxalate may find its way out of the system by the 

 kidneys after it has been taken with vegetable food or with certain 

 medicinal substances. The ordinary rhubarb, or pie-plant, contains a 

 large quantity of calcium oxalate, which, when this article is taken, 

 passes into the urine. It is probable, however, that a certain quantity 

 is formed in the organism. 



Xanthin, Hypoxanthin, Leucin, Ty rosin and Taurin. Traces of 

 xanthin (C 5 H 4 N 4 O 2 ) have been found in the normal human urine, but' 

 its proportion has not been estimated and observers are as yet but im- 

 perfectly acquainted with its physiological relations. It has been found 

 in the liver, spleen, thymus, pancreas, muscles and brain. It is insol- 

 uble in water but is soluble in both acid and alkaline liquids. Hypo- 

 xanthin (C 5 H 4 N 4 O) has not been found in normal urine, although it 

 exists in the muscles, liver, spleen and thymus. Leucin (C 6 H 13 NO 2 ) 

 exists in the pancreas, salivary glands, thyroid, thymus, suprarenal cap- 

 sules, lymphatic glands, liver, lungs, kidneys and the gray substance of 

 the brain. It has not been detected in the normal urine, The same 

 remarks apply to tyrosin (C 9 H n NO 8 ), although it is not so exten- 

 sively distributed in the economy, to taurin (C 2 H 7 NO 3 S) and to cystin 

 (C 3 H 7 NSO 2 ). The last two, however, contain sulphur, and they may 

 have peculiar physiological and pathological relations that are not at 

 present understood. 





