420 



EXCRETION. 



is the case. In comparing the proportion of creatine in the heart and in the muscles of 

 the extremities, in oxen and in the human subject, the quantity has been found to be 

 much less in the heart ; still, the proportion of creatine has been found to be greater in 

 tetanized muscles than in the muscular tissue after repose. 



From the meagreness of our facts with regard to the physiological relations of creatine 

 and creatinine, it is evident that there is much to be learned before we can understand 

 the process of their formation in the healthy organism and the probable results of their 

 retention or deficient elimination in disease. At present we can only say that these prin- 

 ciples are probably produced in greatest part in the muscular tissue. The fact that cre- 

 atine has lately been demonstrated in the brain would lead to the supposition that it is 

 also one of the products of disassimilation of the nervous substance. 



The average daily excretion of creatine and creatinine is estimated by Thudichum at 

 about 11*5 grains. Of this he estimates that 4'5 grains consist of creatine, and 7 grains, 

 of creatinine. 



Oxalate of Lime. This salt is not constantly present in the normal human urine, 

 although it may exist in considerable quantity without indicating any pathological condi- 

 tion. 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 Eobin, a 

 trace may be retained in solution by the chlorides and the alkaline phosphates in the 

 urine. This salt 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 oxalate of lime, which, when this article is taken, 

 will pass into the urine. It is probable, however, that a certain quantity of oxalate of lime 

 may be formed in the organism. Pathologists now recognize a condition called oxaluria, 

 characterized by the appearance of oxalate-of-lime crystals in the urinary sediments ; and 

 sometimes the quantity in the urine is so large, and its presence is so constant, that it 

 forms vesical calculi of considerable size. 



FKJ. 124. Crystals of oxalate of lime, deposited 

 from the normal human urine, on the addition, 

 to the urine, of oxalate of ammonia. (Funke.) 



FIG 125 Crystals of leucine. (Funke.) 



Inasmuch as pathological facts have shown pretty conclusively that oxalic acid may 

 appear in the system without being introduced with the food, some physiologists have 

 endeavored to show how it may originate from a change in certain other of the proximate 

 principles from which it can be produced artificially out of the body. One of the sub- 

 stances from which oxalic acid can be thus formed is uric acid. It remains, however, to 

 show that this can take place in the living organism. Woehler and Frerichs injected 



