366 Journal of Agricultural Research voi. iv, no. 4 



the liquid during operation, and the tenacity with which the bacteria 

 cling to the inner surface of the moist inlet tube. 



The method of determining bacterial precipitation from air by means 

 of exposed Petri plates has been found to be entirely unreliable, as it 

 gives a measure of the number of bacteria-laden dust particles and not 

 a measure of the number of bacteria present. The number of bacteria 

 precipitating upon a given area has been determined by analyzing 

 measured quantities of sterile water which had been exposed to the air 

 for a given length of time in sterile pails. The numbers obtained in this 

 way were from 2 to 32 times higher than those obtained with the plate- 

 exposure method. 



LITERATURE CITED 



(i) Committee on Standard Methods for Bacterial Milk Analysis. 

 1915. Report. In Amer. Jour. Pub. Health, v. 5, no. i, p. 64. 



(2) Committee on Stand.\rd Methods for the Examination of Air. 



1910. Report. In Amer. Jour. Pub. Hyg., v. 20 (n. s. v. 6), no. 2, p. 346-360. 



(3) 



1913. Progress report. In Amer. Jour. Pub. Health, v. 3, no. i, p. 78-86. 



(4) Conn, H. J. 



1914. Culture media for use in the plate method of counting soil bacteria. 



N. Y. State Agr. Exp. Sta. Tech. Bui. 38, 34 p. 



(5) Ficker, Martin. 



1896. Zur Methodik der bakteriologischen Luftuntersuchung. In Ztschr. 



Hyg. u. Infectionskrank., Bd. 22, Heft i, p. 33-52, pi. i. 



(6) Frankland, P. F. 



1888. Methode der bacteriologischen Luftuntersuchung. In Ztschr. Hyg., 

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(7) Hansen, E. C. 



1879-82. Bidrag til Kundskab ora hvilke Organismer, der kunne forekomme 

 og leve i 01 og (Z)lurt. i. Unders0gelser over de Organismer, som til 

 forskjellige Tider af Aaret findes i Luften i og omkringCarlsberg.og 

 som kunne udvikle sig i01urt. /nMeddel. Carlsberg Lab . , Hefte2,p. 

 185-235, 1879; Hefte 4, p. 381-454, 2 fig., 1882. French ed. p. 49- 

 75, 197-218. 



(8) Harding, H. A., Ruehle, G. L., Wilson, J. K., and Smith, G. A. 



1913. The effect of certain dairy- operations upon the germ content of milk. 

 N. Y. State Agr. Exp. Sta. Bui. 365, p. 197-233. 



(9) and Wilson, J. K. 



1913. A study of the udder flora of cows. N. Y. State Agr. Exp. Sta. Tech. 

 Bui. 27, 40 p. 

 (10) and Smith, G. A. 



1909. Milking machines; effect of method of handling on the germ content of 



the milk. N. Y. State Agr. Exp. Sta. Bui. 317, p. 253-292, 4 pi. 

 (II) 



1910. The modem milk pail. N. Y. State Agr. Exp. Sta. Bui. 326, p. 249-281, 



4 pi. 

 (12) H.\rrison, F. C. 



1897. Report of the bacteriologist. In 22d Ann. Rpt. Ontario Agr. Col. and 



Exp. Farm, 1896, p. 105-116, illus. 



