130 MICROBES, 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 crugi- 
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 seeond 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. Mégnin 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. 
