Reaction 1.5 per ct. normal 

 acid to phenolphthalein. 



New Yoke Agricultural Experiment Station. 55 



Plating. — The samples were taken to the laboratory and the 

 plating completed within an hour. The medium used was desig- 

 nated as medium 3.20 and had the following composition up to 

 July 1, 1909, after which the sodium chloride was dropped: 



Beef extract — Liebig . . . 



Sodium chloride 



Peptone — Witte 



Agar 



Lactose, C. P 



Distilled water 1000 c.c. 



The dilutions employed ranged from 1 to 2 to 1 to 1000 depending 

 upon the germ content of the material under examination. 



Incubation and counting. — Since the germs in freshly drawn milk 

 come partly from the udder where they have been held constantly 

 at blood heat and partly from the barn air which is constantly at a 

 much lower temperature, they are not adapted to incubation at a 

 single temperature. 6 On account of this temperature relationship 

 the plates were held five days at room temperature and two addi- 

 tional days at 37° C. and the count here given is that at the close of 

 the second incubation period unless some other period of incubation 

 is specifically mentioned. The construction of incubating chambers 

 in which the desired lower temperatures are constantly available is 

 described in Technical Bulletin 29 7 but these chambers were not 

 available until after the close of these studies. 



The counting was done under a hand lens magnifying four diam- 

 eters. The count here recorded is the average of not less than three 

 and frequently as many as six plates. Occasionally plates present 

 themselves which on account both of the kinds of colonies and their 

 number indicate that some contamination has occurred. These have 

 been omitted from the calculations. 



EXPERIMENTAL DATA. 



OBSERVATIONS ON METHODS OF SAMPLING. 



While there is no well established method of securing samples for 

 bacteriological study from the milk pail it is the almost universal 

 practice to collect such a sample in a sterile test tube as the milk is 

 being poured from the pail. 



c N. Y. Agr. Exp. Station Technical Bui. 27. Page 10. 



7 Conn, H. Joel, and Harding, H. A. An efficient electrical incubator. N. Y. Agr. Exp. Station 

 Technical Bui. 29. 1913. 



