SOURCES OF COMMON MILK BACTERIA . 6 1 



long chains, and it has been suggested that, whereas the pres- 

 ence of these common forms may not render milk suspicious, the 

 presence of the long chains may do so. Upon this matter there 

 is as yet no information. 



It is quite certain that these bacteria get into the milk ducts 

 from the outside. Some have tried to show that they may 

 come from the tissues of the cow, being passed through the 

 gland when the milk is secreted. But while this may be true 

 in case the cow is suffering from some bacterial disease, such 

 as tuberculosis or inflammation in the udder, it is practically 

 certain that this does not occur in normal animals. If we recog- 

 nize that they come from the exterior, it is natural to look for 

 them in greatest abundance just inside of the openings of the 

 teats. They are, indeed, found in the largest numbers just 

 within the teats, where they enter between the successive milk- 

 ings, and, in lesser numbers, further within the gland. They are 

 in just the position to be largely washed out of the ducts by the 

 first streams of milk drawn. This milk, called the fore-milk, is 

 quite sure to contain more bacteria than milk from other por- 

 tions of the milking. During the milking the bacteria may be 

 so thoroughly washed out by the milk stream that the last milk 

 may be quite sterile. Only certain kinds of bacteria appear to 

 be able to live thus permanently in the milk ducts. When the 

 experiment is tried of injecting common bacteria into the 

 ducts, it is found that they do not live long, but completely 

 disappear in a few days. Even the most common of dairy bac- 

 teria, Bact. lactis acidi, are only rarely found in the milk 

 ducts. 1 



Aseptic Milk. The term aseptic milk has been sometimes 

 given to milk drawn from a cow with exceptional precautions, 

 so as to remove as far as possible bacterial contamination. 2 To 



iBurr. Cent. f. Bact., II., p. 236, 1902. 



*Backhaus and Appel. Ber. Landw. Inst. Univ. Konigsberg, p. 73, 1900. 



Willem and Minne. Rev. Gen. d'Lait., iv., p. 121, 1904. 



Lux. Cent. f. Bact., II., xi., p. 195, 1903. 



