130 MICIiOBES, FERMENTS, AND MOULDS. 



B. cyanogenum, which give respectively a yellow 

 or blue colour to milk (Fig. 67). Peasants say that 

 an evil eye has been cast upon the milk, but it is 

 easy to prove that the development of these microbes 

 is due to imperfect cleansing of the tin milk-vessels, 

 since the discolouration ceases when greater care is 

 taken to wash and scald the vessels. 



Bread often displays microscopic growths of a 

 dark green or orange colour, and in this state it 

 cannot be introduced into the stomach without 

 danger. In the first case it is Bacterium cerugi- 

 nosum, in the second Micrococcus aurantiacus. The 

 badly made and badly baked bread of the French 

 peasants, which is often kept for a fortnight or more, 

 exposed to the moisture and heat which favour the 

 development of these microbes, sometimes displays 

 the first of these changes ; the second is particularly 

 common in soldiers' bread, which must likewise be 

 baked several days in advance, and which is conveyed 

 in carts exposed to the weather. Megnin recently 

 observed a cryptogamic growth of this kind on the 

 bread distributed to the garrison of Vincennes. 



The spores of these microbes are found in flour, 

 and resist a temperature of 120, while they are 

 destroyed by that of 140. Thus they are no longer 

 found in the crust, of which the temperature rises 

 to 200 ; but may easily subsist in the much lower 

 temperature of the crumb. Hence the necessity of 

 only using flour perfectly free from germs. 



