2 BULLETIN 642, U. S. DEPARTMENT OF AGRICULTURE. 
may be mentioned. It has long been recognized that an abundance. 
of light is necessary for the production of high-grade milk, but that 
factor must first be placed under a certain group of factors before 
it can be adjudged correctly. Depending upon whether it bears a 
direct relation to the bacterial content of milk or exerts a marked 
influence on the health and comfort of the cattle, it should be erouped 
accordingly. 
In view of these facts, the following group of factors eee been 
selected as a means of dhe the ae 
1. Factors concerned in the production of milk which is practically free from 
visible dirt and which has a low bacterial content. 
2. Factors most directly concerned in the prevention of the infection of milk 
with pathogenic organisms. 
2: Factors of importance in connection with the health of the cattle. 
4, Factors concerned in providing and maintaining conditions suitable for 
the production of a food product, even though they may not directly affect the 
quality of the product. 
It is realized that some factors may enter into more than one of 
the groups above, but their greatest importance can generally be 
assigned to one definite group. For example, the sterilization of 
utensils is of primary importance in the production of milk of low 
bacterial content, but it is also a measure in the prevention of infec- 
tion with sedhgeents organisms. 
This paper considers only the factors in group 1; that is, ee 
concerned in the production of milk practically free from visible 
dirt and of low bacterial content. | 
It is not to be questioned that milk of low bacterial content may be 
produced under conditions in which every possible factor is con- 
trolled, but it is reasonable to suppose that, relatively speaking, some 
factors may be of more importance than others. It may be possible, 
therefore, on the average farm, to produce milk of low bacterial con- 
tent by the combination of a certain few factors which affect the 
quality of milk more than others. Some of the factors have been. 
extensively investigated, and the results of much excellent work per- 
taining to the subject have been published. Such work, however 
g ] I ; y 
has dealt largely with the value of one factor or with the compara- 
tive importance of two or more factors. In our work the problem 
has been studied from a somewhat different angle. 
The endeavor has been to determine methods for the pradenon 
of milk of low bacterial content in the barn of the ordinary type. 
The experimental work was confined to a study of conditions which - 
affect the bacterial content of milk sufficiently to be measured. While 
it is realized that many conditions under which milk is produced 
may affect its quality from a sanitary or economic standpoint, no at- 
tempt was made to study them unless they could be measured in terms 
of the bacterial count. Be ete ane 
nea ie ee 
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