EXPERIMENT STATION WORK RELATING TO PURE MILK. 293 



to the extent necessary to afford any practical protection against 

 milk-borne diseases, neither does it apparently improve the keeping 

 quality of the milk to any very appreciable extent. 



The aeration of milk has been studied at several stations. Wing," 

 Plumb,'' Cooke,'' and Doane "^ have reported experiments and an 

 exhaustive study has been made by Marshall.*' In his experiments 

 Marshall found that the gas content of milk contained, on an average, 

 81.5 per cent of carbon dioxid and 2.42 per cent of oxygen and that 

 aeration reduced the percentage of carbon dioxid to about 35 per cent 

 and increased the oxygen content to about 20 per cent. Among the 

 practical results of his work the following may be noted : Odors and 

 taints may be gretitly reduced by aeration, but this should always 

 be done in a pure atmosphere, in order to prevent in return the 

 absorption of noxious gases by the milk. Aeration does not reduce 

 the number of bacteria nor affect the germicidal action of milk. On 

 account of the increased supply of oxygen, aeration is unfavorable 

 to those fermentations in milk in which toxic substances are pro- 

 duced. Aeration should be conducted at body temperature immedi- 

 ately after milking, be carried out slowly over the most extensive 

 surface possible, and to yield the most satisfactory results be followed 

 rather than accompanied by cooling. Doane's recent experiments 

 showed practically no differences at the end of twenty-four hours in 

 the acid content and number of bacteria in aerated and unaerated 

 samples. 



The prompt and efficient cooling of milk is generally recognized to 

 be of the utmost importance in preventing the development of bac- 

 teria, which, under ordinary conditions, are invariabh^ present in 

 milk as soon as dra'wn. Reference is here made to only two of numer- 

 ous discussions of this subject in station literature. At the Kansas 

 Station Cottrell, Burtis, and Otis f showed by a practical test that 

 with care in milking and handling, cooling immediately after milk- 

 ing to about G0° F., and keeping in cans surrounded with well water, 

 it was possible to keep milk in good condition for forty to fifty-two 

 hours without the use of ice and at a very small cost. In several 

 series of experiments at the Maryland Station ^ milk was cooled in 

 various ways. When cooled immediately to 00° F., milk remained in 

 a condition fit for use for fifteen hours longer than when cooled 

 gradually by setting in running water at that temperahire. A hirge 

 number of such practical tests showed the value of cooling milk im- 

 mediately after milking and of keeping it at a low temperature. 



New York Cornell Sta. Bui. 39. <-■ MifhiRan Sta. Hul. 201 ; Spec. Bui. IG. 



6 Indiana Sta. Bui. 44. ( Kansas Sta. Bui. 88. 



c Vernioiit Sta. Rpt. 1802. p. 12.3. » Maryland Sta. Bui. 88, p. 139. 



i Marjiaud fcJta. Bui. b«, p. 131. 



