107G EXPF-RTAIEXT STATION RECORD. 



coccus Idcticus, wiiicli incrcnsfs frdiii the hc^^'iimiiij;, :iltli<»ii;rli it may be iiiliibitod 

 to some extfiit. 



" Iloatins milk to 5(1° ('. for oO minutes does not entirely destroy the 

 power to restrain the nniltii)lication of bacteria; this power is weakened how- 

 ever, and at 75° C. is destroyed completely. This fact together with the fact 

 that milk serum agglutinates some species of bacteria in vitro to a marked 

 degree seems to favor the assumittion that agglutinins arc in pari responsible 

 for the ai»parent decrease of bacteria in fresh milk, since bactericidal siibstances 

 ar(> destroytnl by heating to 5(5° C. for 30 minutes. 



"The agglutination of certain bacteria in milk serum seems to bear some 

 relation to the apparent decrea.se in numbers of bacteria observed in fresh milk, 

 but this is probably not the only factor causing such reduction." 



The bactericidal property of milk, ,T. S. Evans and T. A. Copk iU)iir. Pcnii. 

 Med. Bill., 21 (1908), No. f), pp. 26-'i~27Jt, fig. 1, charts 8).— The contradictory 

 conclusions of previous investigators on the subject are reviewed, and it is 

 suggested that the varying results may be due to the variation in methods, as 

 none of these investigators employed absolutely sterile milk. The authors 

 obtained sterile milk by drawing milk from the teat with a cannula connected 

 with rubber tubing to a bottle. The following results were obtained: 



" Streptococcus pyogenes. — At the end of 4 hours the bacterial content of the 

 unheated milk had decreased 3.5 per cent; that of the milk heated to 55° C, 

 20 per cent ; that of the frozen milk 7 per cent ; while the pasteurized and 

 sterilized milks had an increase in their bacterial content of 25 per cent and 10 

 per cent, respectively, the bouillon control increasing G per cent. At the end 

 of 8 hours this wide variation in the percentages of increase disappeared. . . . 



"Staphylococcus aureus. — At the end of 4 hours the number of bacteria in 

 raw milk had decreased about 20 per cent ; the milk heated to 100° C. showed 

 an increase of 100 per cent in bacterial content ; in that heated to 68° C. there 

 was an increase of between 10 per cent and 20 per cent ; in that heated to 55° C. 

 there was found an increase of 4 per cent; while in that frozen there was an 

 increase of 40 per cent. The bacterial increase in the bouillon control was 1 

 per cent. . . . 



" Bacillus coU communis. — At the end of 4 hours this organism decreased 40 

 per cent in the count in raw sterile milk, while it increased 10 per cent, 25 per 

 cent, 100 per cent, and 2.000 per cent, respectively, in the counts in the milk 

 heated at 55° C, the bouillon control, the milk heated at 08° C, and the milk 

 heated at 100° C. At the end of S hours the bacterial content increased rai)idly, 

 the raw milk, however, showing the smallest ratio of increase. At the end of 

 24 hours there was very little difference in the percentages of increase in the 

 various specimens. . . . 



" Bacillus acidi lactici. — At the end of 4 hours this organism showed an 

 increase of 6 per cent. 55 per cent, 250 per cent, 1,000 per cent. 3,.5O0 per cent, 

 and 2.500 per cent, resi)ectively. in the bacterial content of the raw sterile milk, 

 the frozen milk, the milk heated at 55° C. the milk heated at 68° C, the milk 

 heated at 100° C, and the bouillon control. . . . 



" Bacillus suhtilis. — At the end of 4 hours this organism showed an increase 

 of 5.5 per cent, 2.5 per cent, 20 per cent, 85 per cent, 4.50 per cent, and 60 per 

 cent, respectively, in the bacterial content of the raw sterile milk, the milk 

 heated at 55° C, the frozen milk, the milk heated at 68° C, the milk heated at 

 100° C. and the bouillon control." 



It would seem from these results that freshly drawn milk possesses a bacteri- 

 cidal activity toward certain micro-organisms and an inhibitory activity toward 

 others. This activity is destroyed at 68° C. and materially impaired at 55° C. 



