740 
duced into the body, too little attention has been given to the ques- 
tion of the number of bacteria in top milk when used for infant 
feeding. Oftimes when infants are taken off breast milk and put on 
modified cow’s milk made from top milk it is found that, in spite of 
various modifications containing var^fing percentages of proteid, the 
milk fails to agree with the infant. In those cases which develop 
diarrhea the fault may not be in the proteid, but in the large number 
of bacteria in the top milk used for the preparation of the formula. 
The gTeater frequency of intestinal tuberculosis in young children 
may be due, not alone to the fact that they use a large amount of 
milk, but because top milk, which contains more tubercle bacilli per 
cubic centimeter than the whole milk, is used in the preparation of 
modified milk formulae. 
The literature upon the subject of the relative number of bacteria 
in top milk and in bottom milk is very slight. Xone of the writers 
seem to have realized the great importance of the subject in its rela- 
tion to infant feeding. 
In 30 samples of milk examined the average number of bacteria 
in gravity-raised cream was 69,211,000 and in the sediment layer 
4,360,000 bacteria per cubic centimeter. 
In 26 samples of milk the average number of bacteria in gravity 
and centrifugally raised cream in the sediment and in the mixed milk 
was — 
Gravity. 
Centrifugalized. 
Whole milk. 
Cream layer. 
Sediment 
layer. 
1 Cream layer. 
Sediment 
layer. 
68, 690, 000 
4,840,000 
96, 840, 000 
18, 840, 000 
14, 388, 000 
In 6 sami^les of milk the average relative number of bacteria in 
the gravity cream was 15,416,000; skim milk, 2,050,000; in the sedi- 
ment layer, 1,405,000; and in the whole milk, 2,708,000. 
In 7 samples of milk the average relative number of bacteria in 
the centrifugally-raised cream was 4,500,000; in the sediment layer, 
725,900; in the skim milk, 119,700; and in the whole milk, 619,800. 
One sample of milk contained 500 times as many bacteria per cubic 
centimeter in the cream as in the bottom milk. 
IITien milk is centrifugalized the great mass of bacteria go uj) with 
the cream; a lesser number is carried down in the sediment. The 
skim milk contains many times fewer bacteria per cubic centimeter 
than the cream or sediment layers. 
Centrifugally-raised cream contains more bacteria per cubic centi- 
meter than the gravity-raised cream from the same milk. 
