On the Diastase of Koji. 



305 



The rise in temperature is almost certainly dne to respiration, a pro- 

 cess common to all plants. I know of no case, however, in which the 

 increase is so great as in the one under consideration. Sachs says that 

 in the spadix of the Aroideaa at the time of fertilisation, and especially 

 in warm air, an excess of temperature of from 4° to 5° C, or even 

 10° C, has been detected.* In the present case the respiration is suffi- 

 ciently active not only to keep the temperature of the rice above that 

 of the surrounding air about 21° F., but at the same time to keep the 

 temperature of the air in the chamber from 30° to 40° F. above that 

 of the air outside, because no artificial source of heat is made use of. 



It is a little remarkable that the variation in the temperature of the 

 air in the chamber is so small, for, as the place is not artificially 

 warmed, but depends upon the heat given out by the growing fungus, 

 it might be expected to be much higher in the morning than in the 

 evening. Such a variation will,, indeed, be noticed, but not to a greater 

 amount than 2° or 3° F. The constancy in the temperature is no 

 doubt the result of having successive batches in the same chamber. 

 During the morning only the actively growing koji is there, and in 

 the evening, when the former is cooling down, a new batch is brought 

 in, which gradually rises in temperature during the night and attains 

 its maximum between 8 and 12 in the forenoon. 



That the growth of the fungus takes place with great vigour is 

 shown not only by the rise in temperature, but by the rapidity with 

 which it removes oxygen from the air. A specimen of the actively 

 growing koji (at 8 a.m.) was placed in a bottle of about 4 litres 

 capacity and well corked. Tubes were arrauged so that a specimen of 

 the enclosed air could be removed from the bottle, and it was then left 

 in the chamber from 8 till 12 noon. Over the koji which was exposed 

 to the air the mycelium of the fungus had developed considerably and 

 had caused the grains of rice to cake together into a solid mass. The 

 rice in the bottle, however, remained quite loose, and no increase in 

 the amount of the mycelium could be observed. Analysis of the air 

 in the bottle showed that the whole of the oxygen had been replaced 

 by carbonic acid. The inference to be drawn from this experiment is 

 that so long as the oxygen was present the mould went on growing, 

 but that the amount of air contained in the bottle was insufficient for 

 its growth, and hence, instead of becoming matted together, the grains 

 of rice remained distinct. 



The diminution in the weight of the rice is considerable. Mr. Jihei 

 Kamayama was good enough to weigh for me the rice used in one 

 operation, and the koji which was formed from it. He found that 100 

 parts of the whitened rice, after being converted into koji, weighed 

 101*3 parts. Samples of each were obtained and the amount of water 



* Sachs, "Lehrbuch der Botanik," 4th edition, 1874, p. 694. 



