482 
a specific bactericidal activity. He does not look upon the reduced 
nmnber of bacteria as a result of the bactericidal activity, but believes 
it to be due rather to a change in the media. 
Moro® denies all bactericidal proj)erties of raw milk so far as the 
cholera, typhoid, and colon bacteria are concerned. This he found 
true of cow’s as well as of woman’s milk. He found, however, that 
the serum of breast-fed children had greater bactericidal properties 
than the serum of children raised on cooked milk. 
Park^ studied this question in 1901 and concluded that freshly 
drawn milk contains a slight and variable amount of chemical sub- 
stances which are capable of inhibiting bacterial growth. At 
temperatures under 50° F. these substances act efficiently, unless the 
milk is filthy, for from twelve to twenty-four hours, but at higher 
temperatures their effect is very soon completely exhausted, and the 
bacteria in such milk will then rapidly increase. Thus the bacteria 
in fresh milk which originally numbered 5,000 per cubic centimeter 
decreased to 2,400 in the portion kept at 42° F. for twenty-four hours, 
but rose to 7,000 in that kept at 50° F., to 280,000 in that kept at 
65° F., and to 12,500,000,000 in the portion kept at 95° F. 
Park,^ 1901, believes this property is too elusive to be of practical 
use in dairying. 
Conn,^ 1903, confirmed the fact that during the first six hours 
there is a dimunition in the number of bacteria in raAv milk, but 
leaves the question open whether we are dealing with germicidal 
properties in raw milk or whether the organisms are simply becom- 
ing more accustomed to their new medium. 
Heinemann ^ reported some investigations upon the subject 
which may reconcile the results of the different writers. He finds 
that for certain species of bacteria there is a bactericidal substance 
in raAv milk while for other species there is none. Moreover, this 
germicidal property does not assert itself after the milk is from five 
to seven hours old. This power is also destroyed after heating milk 
to 56° C. for thirty minutes or by bringing it to the boiling point. 
Stocking,^ 1904, investigated this question by studying the multi- 
plication of certain groups of bacteria, and concluded that many of 
® Moro : Mimcli. mecl. Wocli., yoI. 48, Oct., 1901, p. 1770 ; also Arcli. f. Kinder- 
beilkiinde, vol. 33, p. 435, 1902. 
® Park, William H. : The great bacterial coutamiuatiou of the milk of cities, 
can it be lessened by the action of health authorities? X. Y. Pniv. Bull, of Med. 
Sci., vol. 1, 1901, p. 71. 
c Park, William H. : N. T. Univ. Bull. Med. Sci., vol. 1, 1901. 
^ Conn, W. H. : Bacteria in milk and its products. London, 1903, p. 98. 
^ Heinemann, Paul Gustav : The kinds of bacteria concerned in the souring of 
milk. Chicago, 1903. 
f Stocking, W. A., Jr. : The so-called “ germicidal property ” of milk. Storrs ^ 
Agric. Sta. Bull. 28, 1904, p. 89. 
