SOURCES OF INFECTION IN THE STABLE. 51 



those most injurious to the dairy business, thrive best in 

 darkness, as we shall refer to later on, but it is impossible 

 to clean the cows properly and to conduct the milking 

 properly in a dusky stable. The cow-stable must be lib- 

 erally supplied with clean windows, and in winter-time it 

 must be so arranged that the stable sball be sufficiently 

 lighted morning and evening. If we step into one of our 

 common cow-stables on a winter evening at milking-time, 

 we shall often be surprised to note how the milkers have 

 to grope around in darkness while they perform their im- 

 portant work and handle a material so delicate and easily 

 contaminated as is milk. Under such conditions it is not 

 strange if part of the milk goes outside the milk-pail in- 

 stead of into it, and that the cows are not always clean 

 when the milking begins. It is therefore an absolutely 

 necessary condition for the production of milk that will 

 keep well that the light in the cow-stables be improved; 

 every milker ought, furthermore, to be supplied with his 

 own bright shining lantern. 



Air and Bacteria. As already mentioned, the impure 

 air in the stable is one of the main causes of bacterial in- 

 fection of the milk before it leaves the stable. There is 

 no .difficulty in proving this bacteriologically. The fact is 

 apparent from the experiments above given made in the 

 stable and in the open air, concerning the bacterial infec- 

 tion from the udder and its surroundings (p. 28). Hesse 

 states in his account of the quantitative determination of 

 the micro-organisms of the air, that he found not less than 

 120 bacteria and molds in a liter (quart) of air in a common 

 cow-stable, while the same quantity of air in a dusty school- 

 room, from where the pupils were just hurrying out, con- 

 tained only 80 such micro-organisms. It has been found 



