CHOLERA. 159 



(according to Koch) to the presence of an organic (pyro- 

 malic) acid. Here the acid reaction of the potato is the 

 factor that interferes with the growth of the bacillus, and it 

 is only when the temperature conditions become more 

 favourable than usual that any growth can take place. 



The growth when started appears as a thin, moist " light 

 greyish brown " mass, very similar in character, as Koch 

 points out, to the glanders bacillus as grown on potato, 

 except that it has not the deep or chocolate brown colour so 

 characteristic of that organism. 



A most interesting fact has been observed in this connection. Potato 

 cultivations of bacilli from the various cholera epidemics vary somewhat in 

 colour; there are also other slight modifications in the appearance of 

 the different masses, by means of which a skilled observer, who has 

 cultivated the various organisms from the different localities and epidemics, 

 is enabled to distinguish the bacilli of each epidemic ; and it is stated 

 that in some of the German laboratories the directors can take up half a 

 dozen potato cultivations and say, This is from the Naples epidemic, that 

 from Egypt, and so on through the whole series. There are undoubtedly 

 differences, and to the most inexperienced eye the colour of the Shanghai 

 cholera growth may be seen to differ slightly from that of the Egyptian and 

 that of the Naples growths. 



On blood serum and in milk these organisms grow most 

 luxuriantly. They may cause slight liquefaction of blood 

 serum, but in milk, which forms for them an exceedingly 

 good nutrient medium, they give rise to no noticeable altera- 

 tions ; it may therefore be readily understood how deadly the 

 cholera organism may become if it once finds a resting place 

 in milk. Its presence cannot be recognized by any peculiar 

 or characteristic appearance, by taste, or by smell, as it only 

 gives rise to a faintly aromatic and sweetish smell, which 

 can scarcely be distinguished, except by the most practised 

 nose, from the slightly aromatic smell of the milk itself. 

 Dr. Simpson in The Indian Medical Gazette records a 

 naturally prepared experiment, which shows at a glance 

 what an important part these milk cultivations may play in 

 the spread of cholera. On board the ship Ardenclutha, in 

 port in Calcutta, ten men partook of the milk supplied by a 

 native milk-seller who came to the ship daily ; of these ten 

 men, four died of cholera, and five suffered from exceedingly 

 severe diarrhoea, the tenth, who escaped, had taken only a 

 small quantity of the milk. After careful investigation it 

 was found that the milk had been watered with 25 per cent. 



