272 Mary Davies Swartz, 



The respiratory quotient attains its highest value in the fourth 

 hour, instead of the second or third, showing that cellulose is absorbed 

 more slowly than starch. The rise is too slight to indicate that cellu- 

 lose exercises any considerable protein- or fat-sparing effect. It 

 is unfortunate that the amount of cellulose absorbed was so small. 

 It is striking that the 02-consumption decreases at the very time that 

 the respiratory quotient rises, and the COo-production scarcely in- 

 creases. Lohrisch interprets this as indicating that the increased 02- 

 consumption required for oxidation of the cellulose is compensated by 

 a sparing of protein and fat. The differences seem too small to draw 

 any satisfactory conclusions as to the energy value of cellulose. The 

 low respiratory quotient in the later hours of the experiment, together 

 with the increased Oo-consumption, indicates the utilization of some 

 of the cellulose in the form of fatty acids. We must bear in mind 

 that no formation of sugar or glycogen from cellulose, in men or ani- 

 mals, has been demonstrated. Further investigations would seem to 

 be necessary before we can agree with Lohrisch in saying, " Wir wissen, 

 dass Cellulose und Hemi-cellulosen vom Menschen reichlich verdant 

 werden, wir haben alien Grund anzunehmen, dass ihre Verdauung nach 

 Analogie der Starke ablduf I . . . Die resorhirten M engen werden im 

 menschlichen Organismus vollstlindig verbrannt. Dabei wird Eiweiss 

 und Felt von der Verbrennung geschiitzt.'" In any event, the quanti- 

 ties of cellulose which the alimentary tract of man is capable of ab- 

 sorbing are, apparently, too small for it to play a role of any impor- 

 tance in the diet of a normal individual. 



Occurrence and Nature of Pentosans. 



The anhydrides of the 5-carbon sugars are collectively designated 

 as pentosans. These are not reported to occur in the animal kingdom, 

 but the pentose sugars are found forming a part of the nucleic acid 

 radical of the nucleo-protein molecule. In the vegetable kingdom, 

 pentosans are very widely distributed, as has been shown by many 

 investigators, especially Tollens and his pupils. i They occur in all 

 kinds of plants, from the lowest to the highest, and are limited to no 



1 Tollens, Landw. Vers., V. 39, p. 401, (1891); Tollens, Jour. f. Landw., Vol. 44, 

 p. 171 (1896). 



For an exhaustive review of the literature on the occurrence of the pentosans 

 see V. Lippmann, Chemie der Zuckerarten, 3rd Edition, Vol. I, pp. 44-60; 116-123; 

 and Czapek, Biochemie der Pflanzen, Vol. I, pp. 537-545 (1905). 



