46 



THE CARBOHYDRATE ECONOMY OF CACTI. 



TABLE 9. 



The hydrolysis of the mucilage with 1 per cent hydrochloric acid, and the 

 quantitative determination of the sugars in the usual way, showed, that 34.1 

 per cent was d-glucose and 65.9 per cent was 1-xylose. 



The mucilage prepared as described above always contained a small 

 amount of inorganic ash, from which it was impossible to free it by means 

 of resolution and precipitation with alcohol. It is highly probable that this 

 indicates the presence of a salt of an organic acid of the nature of glucuronic 

 acid or some body akin to the gum acids. 



As to the localization of the mucilage in the cactus and the visible changes 

 associated with its formation, just a few observations were made. Under 

 the microscope in fresh sections of the plant, the mucilage is most clearly 

 visible in special, large cells, distributed throughout the tissue. These cells 

 are two or three times the size of the rest of the cells and are filled with 

 mucilage. When the fresh sections or larger pieces of the cactus are placed 

 in distilled water the mucilage cells swell greatly and finally burst, allowing 

 the mucilage to pass out. By cutting sections from material which had been 

 previously well dehydrated in alcohol and then allowing water or 30 per cent 

 alcohol to flow onto the sections on the microscopic slide, the process of 

 swelling and eventual bursting of the cell can be closely followed. It is 



still an open question whether all 

 the mucilage obtained comes from 

 the bursting of the mucilage cells, as 

 separate experiments have shown 

 that the mucilage is capable of slowly 

 passing through a parchment mem- 

 brane. The behavior of these carbo- 

 hydrates in colloidal solution has not 

 been definitely established. The fact 

 is very generally disregarded that 

 many emulsion colloids exhibit a decided diffusion, though this is, of course, 

 much lower than most crystalloids. Thus, for example, Herzog * obtained 

 the accompanying constants (table 9), using a modification of Graham's 

 method. 



A case of the passage of gum arabic through living membranes exists 

 where this substance is used to keep up the blood volume in animals and 

 is found to be excreted in the urine.* In the case of the flowing of the 

 mucilage from the anesthetized plant it would seem that here the ether, 

 chloroform, or acetone affect the membranes and cell walls so that there is 

 a relatively rapid diffusion. Very recently Lloyd * has devised methods of 

 staining the mucilage cells in situ, showing in a beautiful way the distribu- 

 tion and behavior of these cells and their contents. 



* FREUNDLICH, H. Kapillarchemie. Page 402, 1909. Leipzig. 



*HOGAN, J. J., and MARTIN H. FISCHEB. Zur Theorie und Praxis der Transfusion. 



Kolloidchem. Beihefte, 3, 385-416, 1912. 



HTJBWITZ, P. H. Intravenous injections of colloidal solutions of Acacia in hemor- 

 rhage. Jour. Amer. Med. Assn., 68, 699-701, 1917. 



1 LLOYD, P. E. Year Book, Carnegie Inst. Wash. 1918, p. 72. 



