Nutrition Investigations. 



277 



found that pure xylan was not digested by saliva, gastric or pancre- 

 atic juice, but could be gradually hydrolyzed (in two or three d^ys) by 

 0.2 per cent hydrochloric acid. Bergmann (91) digested pure x>dan 

 with extracts of the intestines of many animals (hen, goose, guinea- 

 pig, sheep, ox, horse), and of the vermiform appendix of rabbits, but in 

 no case found a xylanase. These experiments were performed with 

 suitable antiseptics and controls in all cases. An old experiment by 

 Fudakowski (112), attributing an inverting action upon gum arabic 

 to pepsin, and another by Schmulewitsch (144), attributing such an 

 action upon crude fiber to pancreatin,must be disregarded, as no anti- 

 septics whatever seem to have been used. According to Selliere (152), 

 neither the pancreatic juice of rabbits, nor a mixture pancreatic and in- 

 testinal juices, will hydrolyze xylan. Negative results were also ob- 

 tained by him with macerated intestines of these animals. On the other 

 hand, chloroform extracts of the intestinal contents of rabbits and 

 guinea-pigs fed fresh hay and bread, produced pentoses in a 5 per cent 

 xylan solution after 48 hours digestion at 37 degrees C, while negative 

 results were obtained with boiled controls. This indicates that the 

 enzymes causing hydrolysis were of bacterial origin, a conclusion sub- 

 stantiated by later work of the same author (153). No xylanase was 

 detected in the excreta of carnivora such as the lion, panther, and wolf. 

 From a centrifugalized extract of human faeces and soluble xylan, di- 

 gested under aseptic conditions, xylose was obtained after 15-20 hours; 

 but in meconium of calves and human beings in which bacteria were 

 absent no xylanase could be found, although the intestinal glands were 

 functioning. McCoUum and Brannon (126) have shown that in the 

 case of the cow intestinal bacteria destroy pentosans under anaerobic 

 conditions, the degree of destruction varying with the kind of plant. 

 Corn, wheat and oat feeds were incubated with fecal bacteria of this 

 animal, and digestions continued 14 days in atmospheres both of car- 

 bon dioxide and hydrogen, with the following average results : 



From this review it is evident that the presence of pentosanases in 

 the higher animals has not yet been demonstrated. 



