Nutrition Investigations. 289 



duced when large amounts of this preparation are taken. A slight 

 increase in acetone output, shown in the metabolism experiments 

 with diabetics, points to the same conclusion. Perhaps, as Lohrisch 

 suggests, the very slow digestion of the carbohydrate, may enable the 

 organism to utilize the galactose formed, and account for its non-ex- 

 cretion, but this requires further demonstration. 



According to these experiments by Lohrisch, cellulose and the solu- 

 ble galactan show little difference in their physiological behavior. 

 Both can be digested to about 50 per cent. Ordinary agar, as Saiki's 

 experiments show, is largely recovered in the faeces; in fact, a thera- 

 peutic practice which has been recently established is based upon the 

 recognized indigestibility of agar, namely, its employment as a remedy 

 in cases of chronic constipation. It is especially valuable, as Mendel 

 (196) points out, in those cases where the difficulty is due to an ex- 

 tremely complete digestion and absorption of all foodstuffs from the 

 alimentary tract, which causes the formation of dry, hard faecal 

 masses (scybaUa) difficult to evacuate. The agar, remaining undigested 

 and retaining a high percentage of water, gives bulk and softness to 

 the faeces, and facilitates their daily elimination. Being resistant 

 towards bacterial action, it causes neither gas formation nor produc- 

 tion of harmful decomposition products. According to A. Schmidt 

 (209), it can be advantageously taken in quantities up to 25 grams per 

 day, part with the breakfast cereal, and part with sauce or cream, at 

 another meal. In view of such facts as these, we are hardly prepared 

 to agree with Lohrisch, that ' Cellulose and Hemicelluloses are readily 

 digested. ' 



Occurrence and Nature of Mannans. 



As widely diversified in origin and character as the galactans, and 

 very intimately associated with them are the Mannans. They show 

 all possible degrees of solubility, from the readily soluble mucilage 

 found in certain legumes, to the completely insoluble "reserve-cellu- 

 lose," which forms the horny albumen in such seeds as the date, and 

 which was long confused with true cellulose. 



A few examples will serve to show the diverse places in which man- 

 nans may be found. They occur in yeast :i (258) in algae, as Por- 

 phyralaciniata; (278) in moulds, as Penicillium glaucum; (285) in the 

 leaves and roots of the Japanese plant, Conophallus konjaku (280) ; 

 in the bark and wood of many American trees (272). 



^For further discussion see v. Lippmann, Chemie der Zuckerarten, Vol.1, pp. 641- 

 649, and Czapck, Biochemie der Pflanzen, pp. 325-329. 



