QUALITATIVE ANALYSIS OF MARKET MILK. gi 
TABLE 16. 
Comparison of different culture media, given in percentages. 











: A £ so] a 
c is c Bs) eRe 
v 8 7) we SU 
ie) U O vu Ve 
y o = 5° oD 
g 3 g va an 
Ay Gi n 
Q 5 Pee cis 
Total number, - | 202,000 | IgI,700 | 210,000 | 180,000 | 230,000 
Slow liquefiers aneits VII. ee eee Od i 10.9 II.g LOmE 
Small lob’d colony (micrococcus)} 34.9 Aon 30.9 Soe 30.4 
INO. 222 (Group VIII.), - - Ane, ART 5.9 4.8 3.9 
Group IV.,_ - - - - 123 124 Tent £303 To2 
Group il., - : - - 3,0 22% UsG Boley, Gs3 
Group I., - - - - t20 <0 LO Ler Tar 
iroup Vij - - Leg Le 20 U7 ey 
Rapid liquefiers (Group V VI. oe a2 5 fl! 3 —- 
Group Ill., - - - — ae oi cL — 
Miscellaneous, IN ela = - Loe Gal Eel 9.3 15.5 
Miscellaneous, No. 2, - - — — — ase 2 
Miscellaneous, No. 3, - - ms —_ — — Co 
Undetermined, : 2 = 1.8 740 1473 6 14.6 




species found in milk by the different culture media, and that 
‘the irregularities are less than in Table 14. While there are 
some considerable differences in the percentages given of cer- 
tain species, especially Group IV. and Miscellaneous No. 1, 
they are less than in the experiment represented by Table 14. 
In all of these tables it will be seen that the three or four 
‘miscelianeous species are given at the bottom. These are spe- 
cies present in very small numbers, appearing in some of the 
plates and absent from some others, a condition that would be 
inevitable in the case of a bacterium present in moderately 
small quantities. 
The comparative value of the different media cannot well be 
given by tables. After a long series of tests with media, we 
concluded that the most satisfactory medium for all purposes, 
including both the quantitative and the qualitative analysis, 
was a mixture of the common beef peptone gelatin and the 
gelatin made from milk by the use of rennet. This was chosen 
rather than the custard gelatin, because it is very much easier 
to make and the results were about the same. In all of our 
subsequent work we have used this mixture, with results which 
have been satisfactory. 
= 
