2 BULLETIN 642, U. S. DEPAETMEXT OF AGEICULTUEE. 



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 grouped 

 accordingly. 



In view of these facts, the following group of factors have' been 

 selected as a means of clarifying the subject : 



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. 



3. 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 pathogenic organisms. 



This paper considers only the factors in group 1; that is, those 

 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, 

 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 production 

 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, 



