278 Mary Davies Sivartz, 



DIGESTION AND UTILIZATION OF PENTOSANS BY ANIMALS. 



In the case of men and animals subsisting on a mLxed diet, the hex- 

 oses and their derivatives so overbalance the pentosans, under normal 

 conditions, that the utiHzation of the latter is a question of theo- 

 retical rather than of practical importance. But in the case of herbi- 

 vora, limited to a diet in which pentosans occur in considerable 

 amounts, the extent of pentosan utilization becomes a question of 

 economic importance. It is not surprising to find, therefore, that 

 since the development of satisfactory methods of quantitative deter- 

 mination, a considerable number of investigations have been made 

 upon such utilization by animals. The results of these experiments 

 are shown in tables on pages 274 and 275. 



The results in these experiments were obtained by analysis of food 

 and faeces. Lindsey (123) Gotze and Pfeiffer (113) and Tollens (157) 

 found no measurable amount of pentoses or pentosans excreted in the 

 urine of sheep, but Neuberg and Wohlgemuth (128) state that pento- 

 sans always occur in the urine of rabbits, only disappearing when the 

 vegetable diet is compensated by pentose-free material. They report 

 that 9 per cent of soluble araban (cherry gum) fed to rabbits was ex- 

 creted in the urine. Slowtzoff (154) found 1.4-4.5 per cent of xylan in 

 the urine of rabbits, but no reducing sugar. He also found that if 

 the animal were killed shortly after xylan feeding, xylan could be de- 

 tected in blood, liver and muscles. Hence xylan must have been ab- 

 sorbed from the digestive tract. 



The feeding experiments show that herbivora digest, on the aver- 

 age, 55-60 per cent of the pentosans in their diet, but since no anima,! 

 enzymes hydrolyzing pentosans have been demonstrated, and there 

 is always the possibility of bacterial decomposition in the intestines, 

 the most conclusive experiments as to the actual nutritive value are 

 those of Kellner (118) with the respiration calorimeter. From the 

 slight difference in loss of potential energy, when the furfurol-yielding 

 rye straw preparation was substituted for starch, he concludes that 

 furfurol-yielding substances participate in the formation of fat in the 

 animal body. 



DIGESTION AND UTILIZATION OF PENTOSANS BY MAN. 



We have seen that pentosans can be digested by herbivora to a 

 considerable extent. Can they be digested by man? The only 

 feeding experiments on record are by Konig and Reinhardt (120). 



