Journal of 



Applied Microscopy. 



Volume I. 



DECEMBER, 1898. 



Number 12 



The Persistence of Bacteria in the Milk Ducts of 

 the Cow's Udder. 



Read at the twenty -first annual meeting of the American Microscopical Society, Syracuse, N. Y. 



The constant presence of bacteria in 

 freshly drawn milk is a matter of con- 

 siderable importance. The fact that milk 

 when drawn from the udder may contain 

 bacteria is of the greatest interest in 

 connection with the observance of meas- 

 ures designed to reduce the bacterial 

 content of milk to the minimum. Here, 

 if that fact be true, is one source of the 

 infection of milk which can not be elimi- 

 nated by the exercise of precautions dur- 

 ing the milking or the subsequent pro- 

 cesses to which it is subjected. 



The earlier investigations undertaken 

 to throw light on the question of the 

 presence of bacteria within the healthy 

 udder consisted in counting the bacteria 

 in samples taken during different periods 

 of the milking. Schultz' found a decrease 

 in numbers as the milking progressed. 

 Lehmann' obtained like results. It might 

 be concluded from the work of Schultz 

 and Lehmann that the teats, or at most 

 the lower portion of the cistern, only 

 contain bacteria. 



Gernhardt' found a larger number in 

 samples from the middle of the milking 

 than at the beginning, although some of 

 the samples from the last milk drawn 

 were sterile. To explain his results, 

 Gernhardt suggests that the bacteria 

 make their way up through the milk 

 ducts of the teats, through the cistern, 

 and into the smaller ramifications of the 

 ducts which connect the cistern with the 

 ultimate follicles. Such an assumption 

 explains the wide variation in numbers 

 obtained by him. 



1. Leopold Schultz. Archiv. f. Hygiene, 

 B. S. XIV (1892). 



2. Lehmann. 17te Versammlung d. deut. 

 Ver. f. oflEent. Gesundheitspflege. 



3. Gernhardt. Quant. Spaltpilzunters. d. 

 Milch, Inaug. Dissert. Univ. Jurjew. 



Von Freudenreich* states that, when in 

 the udder, milk is free from bacteria 

 except when the milk glands are in a 

 diseased condition. He mentions the 

 fact as having been demonstrated by 

 Pasteur, who drew samples directly from 

 the cistern by means of a sterile cannula. 

 On the other hand, Bolley and Hall' com- 

 pared the species of bacteria in the milk 

 of several cows, the samples taken 

 through a sterile milking tube inserted 

 into the milk cistern. 



Russell"* found that bacteria are present 

 in the udder proper in case of mastitis. 

 In Russell's Dairy Bacteriology we find 

 the following: " How far these different 

 forms of germ life are able to penetrate 

 into the healthy udder is as yet un- 

 known. In all probability, the glandular 

 tissue of the udder is not affected, 

 although it is possible that microbes 

 might work their way up the open chan- 

 nel of the teat into the udder proper." 



Grotenfelt' says that " Whem the nailk 

 is drawn from the udder of a healthy cow 

 it is germ free, or sterile. The original 

 sterility of normal milk is due to the 

 fact that the bacteria can not gain access 

 to the milk glands from without as long 

 as the udder is not injured in any way." 

 F. W. Woll, the translator of Grotenfelt's 

 work, adds in a footnote: " The bacteria 

 in the milk cistern will be largely washed 



4. Ed. von Freudenreich. Dairy Bacteriol- 

 ogy, translated by J. R. A. Davis. Page 36. 



5. Bolley and Hall. Cent, fur Bakt. und 

 Parasit, II, Abt. I: 795, (1895); Association 

 Ag. Coll. and Exp't Stations (1895); Ab- 

 stract in Experiment Station Record, Vol. 

 VII, No. 11, p. 991. 



6. H. L. Russell. Dairy Bacteriology, pp. 

 42, 43. 



7. Gosta Grotenfelt. The Principles of 

 Modern Dairy Practice, translated by P. 

 W. Woll, p. 23. 



