of two days the plate will show a decidedly spotted appear- 

 ance. These spots may be very fine or very large, according to 

 the kind of bacteria present. Where each speck of dust or dirt 

 or individual bacterium was present a growth will take place. 

 This corresponds in its nature to the growth observed so fre- 

 quently when the housewife puts up jelly and through some 

 mistake fails either to boil it thoroughly or properly cover the 

 top. What has actually happened is that the laboratory worker 

 has planted a little garden, using the jelly as soil and the 

 bacteria in the milk as seeds. Bacteria are really tiny plants or 

 vegetables, and grow readily in such soil as this jelly. It is not 

 necessary to use a microscope, but the resulting growth can be 

 readily seen with the naked eye. By counting the number of 

 spots one estimates the number of bacteria originally in the 

 milk. 



This bacterial testing has been so perfected that it now 

 furnishes a measure of the sanitary excellence of milk. Where 

 milk has been produced in a clean manner and is fresh the 

 number of bacteria will be very small, sometimes as low as 100 

 or even less per cubic centimeter (one-third of a teaspoonful of 

 milk). On the other hand, where milk has been produced in an 

 unclean manner or is stale these numbers may run into millions. 

 By the use of this test it is possible to divide milk into several 

 grades, according to the numbers of bacteria which it may con- 

 tain. The question now is, how good is it possible for the 

 average milk producer to make milk, and what division should 

 be made in establishing such grades? 



Milk inspectors are accustomed to condemn dairies which 

 have barns surrounded by trash and filth, and which have cow 

 stables in which floors and walls and ceilings are dusty, covered 

 with cobw^ebs and accumulations of cow^ dung. Because of this, 

 twenty-five years ago it was commonly believed that only by 

 the establishment of the most model sanitary cow stables was 

 it possible to produce clean milk. This belief led to the wide- 

 spread establishment of certified dairies, in which no expense 

 was spared to make the cow stable a model of sanitary excel- 

 lence, with cement floors and plaster walls, iron stanchions and 

 a complete lighting and ventilating system. Cows in these 

 dairies are groomed twice daily just as carefully as horses are 

 groomed. 



