Chemical Changes in Animal Organism. 311 



example of a method devised for the study of the inter- 

 mediary metabolism in the animal body. 



(D) METHOD BY ADMINISTRATION OF INTERMEDIARY PRO- 

 DUCTS TO SUBJECTS IN WHICH THE METABOLISM IS 

 PATHOLOGICALLY IMPERFECT. 



Certain pathological abnormalities are known, due to 

 the inability of the individual to catabolize completely 

 definite groups. The diabetic subject, for example, is not 

 able completely to utilize the carbohydrates, and excretes 

 dextrose in abnormally large amounts in the urine. In 

 this case the results of this pathological condition are 

 severe, as a large amount of energy derivable from carbo- 

 hydrate combustion is lost, and a general derangement of 

 functions ensues. There are known, however, cases of 

 abnormality in metabolism in which groups of far smaller 

 significance than the carbohydrates are concerned. Amongst 

 such abnormalities may be included the rare conditions of 

 alkaptonuria and cystinuria. In the former case the 

 abnormality (for, as generally it does not lead to serious 

 results to the general health, it can hardly be regarded as 

 a disease) is due to the incomplete metabolism of some of 

 the aromatic products derived from the proteins by hydro- 

 lysis. In the case of cystinuria the metabolism of the 

 cystine derivable from the proteins is incomplete, and this 

 substance is excreted in the urine, and is apt to give rise 

 to concretions in various parts of the body. 



The state of alkaptonuria has been the subject of 

 several exhaustive researches, for although it occurs but 

 very rarely, the conditions existing afford one of the few 

 examples of incomplete metabolism of a very limited 

 number of chemical groups. 



The alkaptonuric condition is characterized by the fact 

 that the urine yields a black coloration when treated with 



