DAIRY FARMING DAIRYING. 183 



The Sharpies milking' machine, H. E. Van Norman (Pennsylvania Sta. Rpt. 

 1913, pp. 163, 164). — In ^ study of the use of a milking machine it appears that 

 one man using two machines secures the greatest efllciency witli a herd of 20 

 annuals, and that as the number falls below this the actual time of the man per 

 cow is increased. One man and two machines apparently can do the work of two 

 hand milkers, and where the number of men required for milking determines the 

 amount of labor on the farm, it is thought the use of the milking machine will 

 be practicable if other circumstances justify the investment. 



Germ content of stable air and its effect upon the germ content of milk, 

 G. L. A. RuEHLE and AV. L. Kulp {New York State Sta. Bid. J,09 {1915), pp. 

 419-474, figs. 4)- — This bulletin is composed of two parts. 



I. Methods of bacterial analysis of air (pp. 422-440). — This material has been 

 previously reported from another source (E. S. R., 33, p. 610). 



II. Stable air as a source of bacteria in milk (pp. 446-474). — In this investiga- 

 tion attention was limited to a study of the contamination due to the general con- 

 dition of the stable air, no attention being given to localized air contaminations 

 that occur in milking due to dirt falling through the air from the cow's body. 

 An attempt was made to control all conditions which might influence the results 

 and to measure the factor of air contamination as directly as possible. An ap- 

 paratus is described which was so constructed as to make it possible to imitate 

 the milking process very closely and yet allowed the use of a sterile fluid in the 

 place of milk as drawn from the udder, which, it has been found, contains vari- 

 able numbers of bacteria. 



It was found that the number of bacteria present in the air of the station 

 stable during such barn operations as milking, feeding hay, grain, and the like 

 usually varies between 50 and 200 per liter of air. Occasionally much lower re- 

 sults were secured and also a few much higher, the highest being 825 per liter. 

 When sterile water was " milked " in the station stable from the apparatus 

 designed for the purpose, the germ content of the liquid was found to average 

 12 per cubic centimeter with a maximum of 73 and a usual range of from 5 to 15 

 per cubic centimeter. 



A large number of tests were made in the stable loft. Here it was easily 

 possible by sweeping up debris from the floor to secure dusty conditions which 

 were as bad as the worst possible conditions obtainable in commercial dairies. 

 When a heavy dust was raised at the beginning of each test the germ content 

 of the air was usually between 1,000 and 2.000 per liter, with an average of 2,068, 

 a minimum of 329, and a maximum of 5,200 per liter. When the dust was 

 maintained continuously throughout the test the numbers obtained in the com- 

 pletely satisfactory determinations averaged 9,575 bacteria per liter of air, with 

 a minimum of 960, a maximum of 28,200, and a usual range of from 2,.500 to 

 10,000 per liter. 



Sterile water milked under these extremely dusty conditions gave an average 

 germ content of 47.6 per cubic centimeter when the dust was raised but once, 

 the highest number being 133, and the usual range between 30 and 100 per cubic 

 centimeter. When the heavy dust was maintained continuously the average 

 germ content of the water milked was 604 per cubic centimeter, with a minimum 

 of 69, a maximum of 1,430, and a usual range of from 300 to 1,000 per cubic 

 centimeter. 



In three commercial stables 58 analyses gave only seven results in which the 

 germ content of the air was greater than the highest count (825 per liter) ob- 

 tained in the station stable, and of these seven only four were decidedly higher 

 than this figure. Milking under the worst of these conditions would, as shown 

 by the work done where an artificial dust was raised, have added from 100 



