478 ISHIZUKA ; ON THE SIGNIFICANCE OF THE NITRATES 



He has also called attention to his observation, that great 

 cholera epidemics appear in those years in which the rain fall 

 of summer remains far below the average, which fact would 

 appear very strange, if the cholera bacillus alone were the 

 cause, as abundance of moisture would be most favourable to 

 the development of that bacillus.' 0 This fact as well as the 

 gradual decrease of the epidemic towards winter/ 2 ' and further its 

 breaking out at the time when the new vegetables are harvested, 

 is in best accordance with the theory of Emmerich and Tsuboi, 

 for which my own investigations above described bring further 

 support. Finally I must point out that the law, discovered by 

 Pettenkofer in regard to the influence of rain, is also confirmed 

 by the phenomena observed in Japan : I compared the intensity 

 of the four cholera epidemics during the last 13 years with the 

 amount of rain-fall from May to October, and from this it becomes 

 evident that in those years in which the rain fall was considerably 

 below the average, the epidemic was more serious than in those 

 years in which the rainfall was more copious, as the following 

 tables show : 



(1) I do not assert here that the nitrites produced are the exclusive poison in cholera. 

 Indeed Ili'tppe and Scholl have discovered in cholera cultures also poisonous proteids. 

 There exist cases of a milder form of cholera in which the formation of nitrites is not the 

 leading factor, as, e.g., also the cholera produced in Guinea-pigs by subcutaneous injec- 

 tions of comma bacilli. Cf. also the interesting article of f/i'ippe, lierl. Klin. Wochenschr. 

 1894. No. 17. 



(2) Montefitsco tries to explain this by the decreasing virulence i:i great cold, but 

 this is not satisfactory, as cholera stops even in warm winters. 



