408 MILK AND MILK PRODUCTS 
microscopic method, no concentration of the bacteria in the sample is 
made. Breed and Brew (1917) compared again, the relation of the two 
counts when studying the application of the microscopic method to the 
control of bacteria in market milk. No general agreement was observed. 
Frost’s method seems to have had little application under commercial 
conditions. Frost (1916, 1917) has carried some studies himself and 
reported a smaller variation with his “little plate’ method than was 
observed with the standard plate. 
The Allen microscopic method may overcome some of the disad- 
vantages of the Breed method. Allen has devised a procedure which is 
said to be applicable to all grades of milk. With the Breed smear gross 
errors are involved on milks with low counts. In his original contribu- 
tion Allen (1916) has shown that on milk with a count of 1000 and 
slightly over, he was able to check the standard plate count very closely. 
Ayers’ Milk Tube Method. This is a very satisfactory method for 
studying the types of bacteria in milk. The milk is plated on agar 
plates which are incubated at 37° C. for six days. After counting the 
plates, each colony should be picked from the plates and transferred 
to a sterile tube of litmus milk. After fourteen days’ incubation these 
tubes are examined and as a result of the reactions shown, the bacteria 
picked from the plates are divided into five groups: the acid-forming, 
acid-forming and coagulating, inert, alkali-forming, and peptonizing. 
Ayers has used this method in studying the flora of different milk 
products. 
Leucocytres IN MILK 
These cells in milk were first given much attention by Stokes and 
Wegefarth (1897). It was noticed that they had much resemblance to 
the white corpuscles and from this it was concluded that they repre- 
sented “ pus” from the cow’s udder. Breed (1914) has given a good 
summary of the literature besides reporting the results of his own inves- 
tigations. He used the direct microscopical method for counting the 
cells first suggested by Prescott and Breed (1911) and later applied to 
the counting of bacteria in milk by Breed (1911). No relationship, if 
any exists, was established between the number of cells discharged and 
bacterial infections of the udders. Breed (1918) reports a milk having 
the enormous number of 54,300,000 cells per cubic centimeter. This 
milk when partaken of was found to have a normal taste and the imbiber 
suffered no evil after effects. 
Stokes’ Method for Leucocytes in Milk. Centrifugal sediments 
from 10 c.c. of milk are stained and examined under the one-twelfth oil 
