DISTURBANCES OF CARBOHYDRATE METABOLISM 295 



and Raper, Levene and La Forge, Zeruer and Waltuch and Alma lliller 

 that in many cases of pentosuria the carbohydrate is certainly not i-ara- 

 binose but is probably d-xyloketose. Thus, there appear to be at least two 

 types of pentosuria, 



Derivation. It was quite natural that pentosuria should be regarded 

 as a manifestation of defective carbohydrate metabolism, and that an 

 attempt should be made to connect its occurrence with that of diabetes. 

 Kiilz and Vogel reported the finding- of small amounts of pentose in the 

 urine of patients with severe and moderately severe diabetes, and these 

 findings were confirmed by W. Voit (1908-9). But the amounts found 

 were always small, never more than 0.2 gram -per day and generally much* 

 less. Kiilz and Vogel also obtained pentosazone from the urine of depan- 

 creatized dogs and of phlorhizinized dogs. It is noteworthy that neither 

 Kiilz and Vogel nor Voit controlled their technic by similar trials with 

 normal urines, with and without the addition of glucose. It appears to 

 the author that their results may have been due to an increased ingestion 

 of pentoses and pentosans, to an increased nuclein metabolism, or to an 

 increased protein metabolism. The significance of the last will be more 

 apparent presently. 



The effect of the ingestion of large amounts of glucose upon the excre- 

 tion of pentose has repeatedly been studied with consistently negative 

 results (Bial(a) (1900), Brat, Erben(d), Klercker, Schiiler, Tinteman). 

 Neuberg(&) (1900) has suggested the derivation of arabinose from galac- 

 tose. The hypothesis does not account for the optical inactivity of the 

 arabinose. Experiments have led to so small an increase in the excretion 

 of pentose after the administration of relatively huge amounts of galactose 

 as to be quite without significance ,(Bial and Blumenthal, Klercker, Luz- 

 zatto, Schiiler, Tinteman). However, in none of these cases is it certain 

 that the excreted pentose was arabinose. It is possible that the ingestion of 

 galactose would increase the excretion of pentose in arabinosuria. 



Experiments with 1-arabinose and 1-xylose (Bial, Erben(d) Tinteman) 

 showed that these pentoses are as well utilized in pentosuria as they are 

 by the normal subject. But the pentose normally excreted by these sub- 

 jects was probably neither 1-arabinose nor 1-xylose. There seem to have 

 been no experiments in which the patient received the same pentose as he 

 was excreting. Such are much to be desired. 



It has also been suggested that the pentose of the urine is derived from 

 that of some of the nucleic acids of the tissues. But feeding large amounts 

 of calf thymus is without effect upon the excretion of pentose (Bial and 

 Blumenthal, Blum(c), Janeway(a), Tinteman), nor is there any other 

 evidence of an increased nuclein metabolism such as would be furnished by 

 an increased excretion of uric acid or of phosphoric acid. The amount of 

 pentose excreted would certainly call for a tremendously exaggerated 



