EXPJOllIMENT STATION BULLETINS. 171 



V. THE CONDITION OF MUAi. IN THE UDDEB. 



For a long time it was supposed that milk in the udder of the cow was free from 

 micro-organisms. This belief was founded upon the fact that some samples of 

 milk drawn under methods which would eliminate contaminations from without, 

 maintained their normal appearance for months. The results, of course, were not 

 always uniform, but if the milk changed, it was supposed that these changes 

 were wrought by accidental contamination. However, upon a closer study of this 

 subject, it has been found that any milk in the udder of a cow contains a variable 

 number of micro-organisms. Ward has made an extensive study of the bacterial 

 content of milk in the udder. He finds several species and a variable number of 

 micro-organisms. Conn, of Connecticut, in estimating the number in a series of 

 tests, places the average number at 267 per cubic centimeter of milk in his so-called 

 aseptic milk. Such milk is doubtless open to outside contamination to some 

 extent. Others, working under similar conditions have gotten results much the 

 same. These germs which are found in the udder belong to different species, and 

 the species are not constant, either in number or kind. We may find germs which 

 do alter milk, and those which do not alter it. Moreover, the number of germs 

 present in milk as it is drawn, will not, as a rule, materially influence the changes 

 in the milk, because it has been found, under practical conditions, that the germs 

 which tend to alter or change the milk are those which enter from without, and 

 the number of contaminating micro-organisms is, of course, in inverse proportion 

 to the cleanliness practiced. 



Usually, therefore, the germs which are present in the milk as it is drawn, may 

 be considered in number as negligible, because those who produce pure milk have 

 demonstrated that the keeping qualities of milk are not seriously interfered with 

 by the germs present. 



VI. THE CONTAMINATIONS OF MILK FBOM WITHOUT. 



1. Hairs. — Those who have studied micro-organisms found upon hairs of ani- 

 mals are well aware of the baneful influence they may have upon the changes 

 in milk. A clean hair may have on its surface from fifty to two or three thousand 

 micro-organisms; a dirty hair, almost any number above this. A dirty hair, there- 

 fore, entering the milk, may provide micro-organisms by the thousand or by the 

 million. If the milk is strained, and the hair kept on the strainer, the micro- 

 organisms go through just the same, and the surface of the hair is simply washed 

 off. If, accordingly, a milker permits a dozen or two hairs to enter the pail 

 during the course of milking, it means that probably millions of micro-organisms 

 have been introduced into the milk. 



Any one at all familiar with the stable is familiar with the character of the 

 dirt on the surface of a hair. There are the micro-organisms which may cause 

 trouble, and are usually capable of producing a variety of changes in milk. They 

 may produce taints or fermentations of any kind. 



In order, therefore, to eliminate micro-organisms from this source, it may 

 be necessary to groom the cow thoroughly or to -clip the hair on her udder. If 

 the cow is kept clean, and is thoroughly groomed, the necessity for clipping is 

 not so great. Further, by dampening the udder during the milking process, 

 the hair may be made to adhere so that it will not fall into the milk. 



2. Dirt. — The dirt that is usually found upon the cow, about the stall, or in 

 the stable, or even on the milker, may contain as many as 80,000,000 germs per 

 gram. About fifty per cent of the dirt that goes into the milk is soluble, the 

 other is insoluble. This latter settles to the bottom. It has been estimated by 

 Backhaus that the people of Berlin consume three hundred pounds of this filth 

 in milk per day. This statement, of course, will assist the reader in understand- 

 ing the amount of dirt that finds its way into the milk. Whether this dirt comes 

 in the form of little particles of dust, or is adherent to straw, hair, hay or food 

 — no matter how it enters, it is this kind of dirt and filth that contains the 

 greatest number of obnoxious micro-organisms. Even in the seams of the milk 

 pail it is possible to scrape out dried dirt and filth thoroughly loaded with these 

 micro-organisms. 



It therefore follows that in order to secure good wholesome milk, we must 

 provide some means of keeping this dirt out. This can be done by means oi" 

 clean clothes and clean hands for the milker, clean dairy utensils, careful man- 



