188 



STATE BOARD OP AGRICULTURE 



counts and that milk powder agar A is next, with meat extract agar 

 the lowest. AVhen samples with 10,000 to 25,000 bacteria were studied 

 the counts upon milk powder agar A are the highest with meat extract 

 agar next and meat infusion agar giving the lowest counts. 



If a preponderance of samples with low counts is present one in- 

 vestigator might be expected to find one medium giving the highest 

 counts while another investigator studying a poorer grade of milk would 

 find that another medium would give the highest counts. 



The 102 samples of milk in Groups I, II, and III gave average counts 

 upon the four kinds of agar as shown in Graph No. I. 



When these samples were divided into groups depending upon the 

 average count upon the four kinds of agar the medium giving the highest 

 counts for the different groups is indicated in Table II. 



TABLE II 



Number of bacteria per c e. Average with 4 kinds of agar 



Under 10,000 



10,000— 2.'>,000 



25,000— 50,000 



,50,000— 100,000 



100,000— 200,000 



200,000—1,000,000 



Over 1,000,000. ... 



Highest average 

 With 



Bacto agar 

 Agar A 

 Baeto agar 

 Baetn agar 

 Bacto agar 

 Agar A 

 Baeto agar 



Next highest 

 With 



Agar A 

 Extract agar 

 Agcr A 

 Agar A 

 Agar A 

 Infusion agar 

 Agar A 



Next lowest 

 With 



Infusion agar 

 Bacto agar 

 Infusion agar 

 Infusion agar 

 Infusion agar 

 Bacto agar 

 Extract agar 



Lowest Average 

 With 



Extract agar 

 Infusion agar 

 Extract agar 

 Extract agar 

 Extract agar 

 Extract agar 

 Infusion agar 



The average bacterial count of samples tabulated in Groups No. 

 I, II and III when arranged according to their pH scores indicates 

 that while the pH score does not check with the bacterial count in many 

 cases, it does check in a general way. Samples scoring T5, 70, 65, 60, 

 and 55 because of the small numbers of samples in the various groups 

 do not check when taken separately but do check when arranged to- 

 gether as shown in Table No. III. 



The samples of milk scoring 5(K, 45, and 40 show a decrease in bacterial 

 count. This is probably due to the fact that some of the inert types find 

 the increased activity of the acid bacteria unfavorable. 



This table does not include the nine samples of milk in Group III 

 which were incubated at 37° F. or the tw-o samples of pasteurized milk 

 in Group I. 



TA-BLE NO. Ill 

 Showing the relation of average bacteriological counts and average of pH scores. 



Number of Sample 



7. 

 10. 

 10. 



4. 

 10. 



8. 

 13. 

 14. 

 13 



2. 



