PENTOSURIA IN DIABETES 289 



synthetical processes, it is also not very probable a priori 

 that the pentoses are destroyed (as by fermentation in the 

 intestine) to such an extent as to be entirely lost as sources 

 of energy for the body. 56 While herbivora are able to con- 

 sume considerable quantities of pentoses, the human assim- 

 ilation limit for these sugars (although man always destroys 

 in his economy at least a part of any large amounts which 

 have been ingested) is strikingly low; so much so, in fact, 

 that even after ingestion of a single gram or a fraction of a 

 gram of xylose, arabinose, rhamnose, etc., the pentose 

 reactions may become positive in the urine. 



Alimentary Pentosuria. There is no wonder, therefore, 

 that an alimentary pentosuria of low grade (as indicated by 

 the studies of F. Blumenthal and others), particularly after 

 indulgence in fruits (cherries, plums, apples) and other 

 vegetable materials, is met with appreciable frequency. 



Pentosuria in Diabetes. It should also be easy to under- 

 stand why a small amount of a pentose may be found mixed 

 with the glucose in the urine of severe cases of human 

 diabetes and of the dog in pancreatic diabetes, as was proved 

 by E. Kiilz and J. Vogel. The nature of this sugar with 

 five carbon atoms is apparently not well known, and in fact 

 its optical activity never seems to have been tested. 57 One 

 would probably not be far wrong in supposing that a portion 

 of the tissue pentoses, which are set free from the nucleo- 

 proteins in the breaking down of the tissues, can make their 

 appearance in the urine. This idea is not contradicted by 

 the fact that it is not possible to recognize by analysis a 

 pentose impoverishment of the tissues in connection with 

 pancreatic diabetes and phloridzin diabetes in animals. 58 



60 Literature upon Pentosans as Foods: A. Magnus-Levy, 1. c., pp. 396-398. 



OT C. Neuberg, Handb. d. Pathol. d. Stoffwechs., 2d ed., 2, 223, 1907; cf. 

 also W. Voit (Sandmeyer's Sanatorium), Zeitschr. f. physiol. u. diat. Ther., 

 12, 659, 1909. 



58 S. Mancini (Siena), Arch, di Farmakol., 5, 309, 1906, cited in Centralbl. 

 f. Physiol., 20, 642, 1906; cf. also L. Caminotti, Biochem. Zeitschr., 22, 106, 

 1909. 



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