IV. CONCLUSIONS. 



1. The hemicelluloses of the ten species of marine algae included 

 in these investigations are chiefly pentosans and galactans. The pen- 

 tosans are largely insoluble in water, but a soluble form in consider- 

 able quantity has been isolated from Rhodymenia palmata. The ga- 

 lactans are soluble in hot water, and are characterized by their gela- 

 tinous nature. Small quantities of soluble pentosans have been found 

 associated with them in every case. 



2. In order of resistance to the action of bacteria, the hemicellu- 

 lose groups studied stand as follows, — galactans, pentosans, levu- 

 lans, mannans, the galactan of Chondrus crispus being entirely unaf- 

 fected by common micro-organisms. 



3. Aerobic and anaerobic cultures of soil and faecal bacteria, and 

 cultures of B. anthracis symptomatici and B. maligni oedematis, caused 

 inversion of salep mannan, with actual production of reducing sugar. 

 The latter cultures also hydrolyzed the pentosan of Rhodymenia pal- 

 mata, and the levulan, sinistrin. In a mixture of aerobes, salep ap- 

 peared to be partially hydrolyzed, forming an insoluble transition 

 product. 



4. Digestion experiments in vitro, continued for 24 hours at body 

 temperature under antiseptic conditions, have been almost entirely 

 negative in result. The only exceptions are the hydrolysis of the pento- 

 san of dulse, the galactan of limu kohu, and the levulan, sinistrin, 

 by "Taka" diastase; and of sinistrin, and the galactans of Hmu kohu, 

 limu akiaki, and slippery elm bark, by artificial gastric juice or 0.2 

 per cent hydrochloric acid, the action of the gastric juice being in all 

 probability due to its acidity. 



5. After parenteral injection, whether subcutaneous or intra- 

 peritoneal, the hemicelluloses are excreted through the kidneys, and 

 can be recovered unaltered in the urine. The pentosan of dulse is 

 completely eliminated in four to five days, and the carbohydrates of 

 Irish moss, salep and sinistrin, in one to three days. 



6. Feeding experiments show that those hemicelluloses most 

 readily attacked by bacteria disappear most completely from the 

 alimentary tract. The average coefficient of digestibility for man is, 

 in the case of the pentosan of dulse and the mannan of salep, 99 per 



363 



