Decembeb 27, 1912] 



SCIENCE 



'8S5 



the fruit, the methods losed by Grore" and 

 as here outlined, when this desideratum 

 will be compassed. 



Having justified the scientific method 

 from the practical point of view, as I be- 

 lieve to have been done, may I finally ask 

 your attention to the further question which 

 you will be sure to ask, namely, why car- 

 bon dioxide should act as it does. "Why 

 should a fruit which would remain under 

 normal conditions inedible for its bitter- 

 ness during a month or more, become quite 

 edible in a week with a single dose of a cer- 

 tain gas, in 36 hours if the dose is doubled 

 and in 15 hours if quadrupled? Let me 

 prepare your minds for the answer by re- 

 minding you of the very familiar fact that 

 it takes a good deal longer to cook an egg 

 to hardness if a temperature considerably 

 below boiling point is used than if it is sub- 

 jected to 212 degrees or over. "With this 

 in mind, our attention may be directed to a 

 few points concerning the structure of the 

 fruits of which we have been speaking. 



The edible flesh or pulp is composed of 

 a great number of minute cellulose sacs 

 (cells) each containing its quantum of liv- 

 ing material as an inner lining, and this in 

 turn filled with sap which is water with 

 varying amounts of substances, such as 

 mucilage, sugars, and salts, in solution. 

 In both the persimmon and in the date, 

 these sacs are of two quite distinct kinds, 

 those from which tannin is absent, and 

 which are relatively small; and those in 

 which tannin occurs admixed with other 

 substances in the sap. The tannin sacs are 

 quite large, and may be readily distin- 

 guished by the unaided eye. You may see 

 them in the ordinary dried dates of com- 

 merce as a layer of clear brown particles 

 just beneath the somewhat tough skin. 

 The color, however, is due to the oxidation 

 of the tannin — in the fresh condition they 



'BuUs. 141, 155, Bur. Chem., V. S. Dept. Agri. 



are colorless, and can be recognized only by 

 special means, that is, by applying suitable 

 reagents which cause color changes in the 

 tannin. 



If now we choose a persimmon which 

 softens before it loses its astringency, it is 

 possible to isolate from the pulp single tan- 

 nin sacs, which may then be examined 

 under the microscope. If uninjured — if 

 the cellulose membrane is not ruptured — 

 the watery contents will glisten with a 

 satiny sheen. On adding water so that the 

 tannin sac is surrounded by it, the sac ab- 

 sorbs water and bursts, and the contents 

 ooze out. This simple fact of bursting in 

 consequence of the absorption of water 

 proves conclusively that there is something 

 more than tannin present, as tannin in so- 

 lution can not absorb water sufficiently to 

 produce such an effect. Sugar or salts 

 might, if in sufficient quantity ; but we can 

 prove in another way that the substance in 

 question is of neither of these classes of ma- 

 terial, for it is capable of coagulation, in 

 much the fashion that, as every housewife 

 knows, we may coagulate jelly by cooling it, 

 or an egg by boiling it. In the ease of our 

 tannin sac material, we may use heat, or a 

 variety of chemical substances. Of these I 

 shall, for the present purpose, mention but 

 one class, namely, the alkaloids, such as 

 antipyrine, quinine, etc. If a solution of 

 any of these be applied in the room of 

 water, the jelly-like mass may swell some- 

 what at first, but soon becomes hard and 

 rigid, giving off water and shrinking ac- 

 cordingly. At the same time, however, 

 within the interior of the coagulated mass 

 there appears a coarse white granulation, 

 which is caused by the union of the alka- 

 loid with tannin within the jelly. This re- 

 lation of tannin to the jelly is brought out 

 still more strikingly if we examine, in the 

 same way, a tannin sac which has been 

 taken from a fruit which has become nearly 



