30 THE CARBOHYDRATE ECONOMY OF CACTI. 



A quantity of the dried cactus material was mixed with water and boiled 

 for 2 hours, cooled, a solution of taka-diastase added, and kept at 37 for 

 22 hours. This procedure was repeated for 8 days, each time adding fresh 

 taka-diastase, and at the end of this time the small pieces of cactus, after 

 treatment with alcohol and iodine in the usual manner, still showed dis- 

 tinctly the presence of starch. The slime of the cactus was quite unaffected 

 by this treatment. A quantity of corn starch treated in a similar manner 

 was completely hydrolyzed after the first day. It appears, therefore, that 

 the slime in some manner protects the starch against the action of the taka- 

 diastase. It is evident that plant material containing such mucilaginous 

 substances offers some unusual difficulties and is not amenable to the ordi- 

 nary methods of analysis. These slimes are very readily hydrolyzed by 

 dilute acids ; by such treatment they lose entirely their mucilaginous char- 

 acter and the solutions can be easily filtered. 



Cellulose was determined by taking the residue from the acid hydrolysis, 

 digesting it with 1.25 per cent KOH, washing thoroughly, and filtering 

 through a tared filter-paper and drying. The dried mass was then incin- 

 erated in a crucible and the ash subtracted from the total weight of the 

 crude fiber. The first determinations were made by use of the chlorination 

 method, 1 but as the differences between this and the much simpler method 

 just described were found to be very slight and within the experimental 

 error of either method, the first procedure was followed, which yielded 

 results that had at least a comparative value. 



CALCULATION OF ANALYTICAL DATA. 



The analyses were calculated in terms of cubic centimeters of standard- 

 ized Fehling's solution reduced, per gram of dry sample. The following 

 deductions represent the various sugars. In the solution of the acid 

 hydrolysis the copper values are distributed as follows: 



A. Total sugars of the hydrolyzed material, i. e. f the monosaccharides as well as 



the hydrolyzed polysaccharides. 



B. Fermented residue of A, or total pentose sugars, including monosaccharide 



pentoses and pentosans. 



In the alcoholic extraction : 



C. Monosaccharide hexose and pentose sugars. 



D. Hydrolyzed product of C or inverted disaccharides, original hexose, and 



pentose. There are no disaccharide pentoses present. 



E. The fermented residue of D or monosaccharide pentose. 



Then the copper value of the various sugars are : 



A. Total sugars. C. Monosaccharides. 



A-D. Total polysaccharides. D-C. Disaccharides. 



D-E. Disaccharides plus hexoses. C-E. Hexoses. 



A-B. Total hexose sugars. B. Total pentoses. 



(A-B)-(D-E). Hexose polysaccharides. E. Monosaccharide pentoses. 



B-E. Pentosan. 



1 CBOSS, C. F., and E. S. BEVAN. Cellulose. Page 94, 1895. London. 



