1917] DAIRY FARMING — DAIRYING. 775 



ments are given of information received from 31 States and 102 cities concern- 

 ing methods of appointment and compensation of dairy and milk inspectors. 



Reliability of the bacteriological analysis of milk, H. W. Conn (Milk 

 Dealer, 6 (1917), No. 4, pp. 50-56). — In this paper, read befoi-e the International 

 Association of Dairy and Milk Inspectors at Springfield, Mass., the author dis- 

 cusses the reliability and significance of bacteriological milk analysis. A sum- 

 mary is given of an extensive series of tests made during the last three years 

 in a considerable number of laboratories to determine the amount of variation 

 in the analysis of milk that may be introduced by conditions beyond control. 



The results of 20,000 analyses show that by standard methods used in rou- 

 tine laboratories by ordinary laboratory assistants variations of from 25 to 30 

 per cent in the analysis of identical samples of milk may be expected to occur. 

 Where special care is taken by experts a much closer result is obtained. How- 

 ever, in view of the enormous range in number of bacteria occurring in different 

 samples of milk this amount of variation in the results of bacterial counts is con- 

 sidered of no real significance. "A bacteriological analysis of milk can not be 

 relied upon to give actual numbers of bacteria, but only approximate num- 

 bers. . . . 



" The bacteriological analysis of milk is not to be taken as indicating in itself 

 either a condition of safety or a condition of danger, but only as a warning. 

 Good, clean, fresh milk will have a low bacterial count, and a high bacterial 

 count means dirt, age, disease, or temperature. A high bacterial count is there- 

 fore a danger signal, and justifies the health ofiioer in putting a source of sup- 

 ply with a persistently high bacterial count among the class of unwholesome 

 milk. 



" B:icteriological analysis offers the only means of grading milk according 

 to its sanitary character. A grading system applied to the milk industry is the 

 great desideratum for the improvement of the industry in the future from the 

 standpoint of the producer, the dealer, and the consumer." 



Why cream tests vary and how to produce first-grade cream, E. O. Chaltts 

 {Union So. Africa In, it. Agr. [Puh.], 82 {1915), pp. 21, figs. 9).— The autlior 

 explains the various points connected with the successful operation of cream 

 separators and reports the results of several series of tests with a 45-gal. sepa- 

 rator to ascertain the cause of vai'iations in cream tests. 



In testing the effect of variations in the speed of separators, using milk test- 

 ing 4.3 per cent fat and separating at a temperature of 86° F., it was found 

 that turning the handle 60 revolutions per minute, the prescribed speed, gave 

 cream testing 54 per cent fat and turning at 55, 50, and 45 revolutions per 

 minute, gave creams testing 46, 31, and 26 per cent, respectively. Irregular 

 turning produced cream testing 44 per cent fat. In separating milk testing 3.5 

 per cent fat at 86 to 90° when the separator handle was turned at 60 revolutions 

 per minute, cream containing 34 per cent fat was obtained, and when turned at 

 74 and 40 revolutions per minute 52 and 20 per cent creams, respectively, were 

 obtained. Turning the handle irregularly produced 27 per cent cream. 



In a test in which milks of different fat contents were separated under iden- 

 tical conditions, the separator being turned at 60 revolutions per minute and 

 the milk separated at 88°, milk testing 4.8 per cent fat produced 49 per cent 

 cream, and milk testing 2.9 per cent produced 38 per cent cream. 



The final experiment had to do with the effect of temperature of the milk 

 upon the fat content of the resulting cream. Using 3.7 per cent milk and turn- 

 ing the separator at 60 revolutions per minute, milk separated at 90° produced 

 42 per cent cream, and milk separated at 80 and at 74° produced 51 and 52 per 

 cent creams, respectively. 



Notes are given on the care of cream on the farm. 



