6 The Plaistt World. 



difference in that the tannin reaction with iron chloride fades 

 away into the usual dirty brown more readily in tannin-gelatine 

 In the tannin masses the browning follows on boiling, and then 

 occurs superficially. This, however, could be explained on the 

 ground that the carrier in the tannin-cells is not a gelatin. As 

 regards the physical appearance and its behavior toward de- 

 hydrating agents, and conversely, the tannin-gelatine simulates 

 the tannin-masses so completely as well-nigh to deceive the ob- 

 server. The recovery of form on release of pressure under the 

 cover-glass, and the fragmentation, seen by Howard in the 

 tannin masses, are very similar. The progressive friabler.ess in 

 the latter is relative to the amount of dehydration, and denotes, 

 probably, nothing else. After a certain degree of solidity has 

 been reached so that the tannin-masses remain intact when ob- 

 served in water, further change may be obviated at any point 

 simply by isolating the tannin cells by shaking and decantation. 

 I have kept them three weeks or longer and no change was ob- 

 servable, in distilled and tap water. On the other hand the 

 changes in question take place during digestion with pepsin in 

 vitro or in the digestive tract, independently of the fruit .(^gs 

 9, 10). 



If, on the other hand, we examine the contents of the tannin 

 cells previous to the point at which the tannin-masses are able 

 to maintain their integrity, the cells, when placed in water or 

 saliva, will burst, and, as Howard has properly put it, the con- 

 tents "mingle" with the surrounding fluid. But we have to 

 note that although they mingle, the resulting mixture is of the 

 same nature as a thin, well-cooked starch-water mixture. This 

 can be shown by the addition of iodine, which at once coagulates 

 the cell-contents, and one then observes them as stringv masses 

 throughout the water. The negative results obtained on treat- 

 ing with iodine a strong solution of tannin (commercial) impris- 

 oned by cotton fibers, seems to indicate that the fluid which es- 

 capes from the cells is not a simple tannin solution in water but 

 that it is a loosely combined tannin-substance analogous to 

 tannin-gelatin. A granular appearance which is visible after coagu- 

 lation with iodine supports this conclusion, since iodine fails to 

 produce the same granulation with tannin. 



If a small piece of the pulp of a hard, unripe fruit be mounted 

 in strong sugar solution and crushed to expel the contents of 



