CALCIUM OXALATE. 



383 



sulphuric. When boiled for a long time with barium hydrate, it is changed 

 into urea and sarcosine. When boiled with the strong acids, creatine loses 

 an atom of water and is converted into creatinine. This change takes place 

 very readily in decomposing urine, which contains neither urea nor creatine, 

 but a large quantity of creatinine, when far advanced in putrefaction. 



Creatinine is more soluble than creatine, and its watery solution has a 

 strongly alkajine reaction. It is dissolved by eleven parts of cold 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 substance is one of the most 

 powerful of the organic bases, readily forming crystalline combinations with 

 a number of acids. According to Thudichum, creatine is the original excre- 

 mentitious substance produced in the muscular substance, and creatinine is 

 formed in the blood by a transformation of a portion of the creatine, some- 

 where between the muscles and the kidneys ; " for, in the muscle, creatine 

 has by far the preponderance over creatinine ; in the urine, creatinine over 

 creatine." The fact that creatine has been found in the brain would lead to 

 the supposition that it is also one of the products of disassimilation of the 

 nervous tissue. 



The average daily excretion of creatine and creatinine was estimated by 

 Thudichum at about 11*5 grains (0*745 gramme). Of this he estimated that 

 4-5 grains (0-292 gramme) consisted of creatine, and 7 grains (0-453 gramme) 

 of creatinine. 



Calcium Oxalate. Calcium oxalate (oxalic acid, C 2 H 2 4 ) is not constantly 

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



Fio. 125: Crystals of calcium oxalate, depos- 

 ited from the normal human urine, on the 

 addition of ammonium oxalate to the urine 

 (Funke). 



FIG. 126. Crystals of leucine (Funke). 



without indicating any pathological condition. It is exceedingly insoluble, 

 and the appearance of its crystals, which are commonly in the form of small, 

 regular octahedra, is quite characteristic. According to Neubauer, 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, 



