Decembee 27, 1912] 



SCIENCE 



883 



paper umbrellas and similar services^ — 

 examples of the preserving effect of tannin. 

 The peculiar properties of kaki-no-shibu, 

 however, as the Japanese chemist Ishikawa 

 suspected years ago, is not due to the tan- 

 nin content alone, but to the joint action, 

 as I believe, of the tannin and another sub- 

 stance of mucilage-like character with 

 which the tannin is combined much as it is 

 with hide to make leather. 



"We are concerned here, however, with 

 those edible sorts which do not become non- 

 astringent without at the same time soften- 

 ing. These when quite ripe can only by 

 courtesy be called edible — decayed would 

 better describe their condition. They have 

 lost a fine aroma and a delicate sweetness 

 which, coupled with a crisp firmness, 

 would, in the absence of tannin, make up 

 the qualities of a delicious fruit, as those 

 know who have eaten them after being 

 ripened artificially either in Japan or at 

 home. This is accomplished by the Japan- 

 ese, as it has been for centuries doubtless, 

 by packing the hard, unripe fruit in freshly 

 emptied tubs, in which sake, the national 

 whisky of that people, has been kept. A 

 fully packed tub is tightly closed and the 

 contained air in them displaced^ by blow- 

 ing through a small hole, the air escaping 

 by another. The openings are then 

 plugged so that the package is made air- 

 tight. In the course of a few days, the 

 length of time depending upon the variety 

 under process, the fruit becomes edible 

 without losing its firmness. This hasten- 

 ing of one of several independent processes, 

 spoken of collectively as ripening, result- 



^ Bishop Heber Hamilton informs me that kakl- 

 no-shibu is used also for painting exposed wood- 

 work, but is efficient only for a year. When ap- 

 plied it is colorless, but turns red in a few days — ■ 

 evidently by oxidation of the tannin. 



' According to some accounts, this is done when 

 reclosing the package after it has been opened to 

 test the fruit. 



ing in non-astringency, has been regarded 

 as due to the action of some constituent of 

 the sake, with which the wood of the cask 

 is of course soaked. This may be either 

 the alcohol or a slight amount of acetic 

 acid. I have argued, from experimental 

 data, that it is the alcohol which, by stimu- 

 lating the fruit to respiration in excess of 

 the normal, quickly causes a formation of 

 carbonic acid gas in addition to that which 

 is introduced by the breath. At any rate, 

 there is little doubt that the carbonic acid 

 gas is the active agent, since Gore, of the 

 Bureau of Chemistry, U. S. Department of 

 Agriculture, found that certain varieties 

 of persimmons grown in the United States 

 could be treated with carbon dioxide at 

 normal pressure with results quite similar 

 to those obtained by the Japanese with 

 their ancient but empirical method. Gore's 

 experiments were in part repeated by my- 

 self at the State Experiment Station of 

 Alabama, with like outcome. It was found 

 that the variety known as Hyakume^ grown 

 on the station grounds if exposed for about 

 eight days to an atmosphere of pure car- 

 bon dioxide, loses its bitterness while still 

 remaining firm and crisp, and retaining its 

 aroma and sweetness. The fruit so treated 

 was most excellent to the taste, as testified 

 to by a number of persons whose skepti- 

 cism regarding the edibility of a hard per- 

 simmon had been begotten of much experi- 

 ence, and whose testimony was therefore of 

 the greater value. 



At this point a question arose. If a pure 

 atmosphere of carbon dioxide at ordinary 

 pressure induces the already described re- 

 sult, why should not an increased dosage 

 effect the same result more rapidly? To 

 attain to the answer I exposed the same va- 

 riety of fruit to twice the amount of the 



* There are two varieties of Hyakume recog- 

 nized, one of which is astringent until softening 

 intervenes, while the other loses its astringency 

 while still firm. 



