DAIRY INSPECTION 147 
effect of sunlight is not fully appreciated. Experiments 
with artificial cultures of various bacteria have shown 
that direct sunlight is very destructive to germ life, while 
the action of diffused light, although less powerful, is also 
quite effective. Tubercle bacilli are killed by direct sun- 
light in a few hours, while even diffused daylight destroys 
them in a few days (Koch). 
Direct sunlight kills anthrax 
spores in five hours and the 
bacilli in thirty hours, spores _, 
being more susceptible to # 
sunlight than bacilli (Ar- ff 
loing, Roux). Direct sun- 
light destroys or decreases 
the virulence of colon bacilli, 
the bacilli of fowl cholera 
and swine erysipelas, and the 
virus of hog cholera, while 
diffuse daylight also exerts 
a similar but less powerful 
action (Neumark). 
The inspector should | 
note the location and size of | 
the windows and determine 
the total square feet of win- f 
dow surface. He should ; 
also observe whether the 
glass is clean and if other buildings obstruct the en- 
trance of light. Three to four square feet of win- 
dow surface for each cow will usually admit sufficient 
light, provided the windows are properly placed and 
equally distributed. In cold climates, an excess of win- 
dow surface may increase the radiation of heat to such an 
Fig. 12.—Window arranged to act as a fresh 
air inlet (Wis. Exp. Sta. Bull. No. 266). 
