8 
IMPERIAL COLLEGE OF 
of sodium, in that the more potash is consumed, the more 
soda appears in the excreta. As a consequence thereof, 
says Bunge, people whose diet includes much vegetable 
food which is generally rich in potash, necessarily consume 
a comparatively high quantity of common salt to replace 
the loss of soda. Now the ordinary Japanese diet is, in¬ 
deed, largely made up of vegetables rich in potash, such as 
roots, tubers, young legumes, and tea, and thus creates a 
predilection for salted foods (■ miso, shoyu, and vegetables, 
especially raddishes, pickled in salt water). 
Experience has taught the Japanese farmer not to 
apply human excreta in the fresh state to his crops, but 
to allow the manure to undergo a thorough putrefaction or 
fermentation before it is used. For this purpose it is 
diluted with a 2-3 fold volume of water and kept in large 
wooden tubs for about 10 days during the cold part of the 
year, and for about 5-6 days during the warm season. 
When a greenish colour makes ' its appearance on the 
surface of the dung, the decomposition is regarded as 
complete, and the manure is then ready for application. 
During this period of putrefaction and fermentation of the 
diluted night-soil, as well as while storing unmixed excreta 
before using them, a deep disintegration of the organic in¬ 
gredients is effected by the vigorous growth and enormous 
increase of the minute fungi which are contained in the 
fæces and enter the excreta along with atmospheric dust ; 
a considerable proportion of the organic substance is de¬ 
stroyed, escaping into the air, in the form of carbon dioxide 
and marsh gas ; the urea, the principal nitrogenous consti¬ 
tuent of the urine unites with water, and is converted into 
ammonium carbonate ; and, in consequence, the reaction of 
the urine, which is acid when it leaves the body, turns al¬ 
kaline ; owing to this latter change, various substances of 
the fæces, especially biliary products are dissolved, and 
confer a dark brown or greenish colour on the dung. 
