432 MILK AND MILK PRODUCTS 
cheese tryer. Cut a number of thin slices from different parts of this 
plug and weigh out 1 gm. of these slices on a flamed copper foil using 
an analytical balance. This sample should be triturated in a flamed 
mortar with 10 gms. of sterile granulated sugar or finely ground ster- 
ilized quartz. Care should be taken to have the room free from dust 
and the instruments which come in contact with the cheese, sterile. 
Dilute this freshly ground cheese to 30 c.c. with sterile water. An 
aliquot portion should be transferred to a water blank. Plate out in 
litmus whey gelatin in dilutions of from 1000 to 1,000,000 or there- 
abouts. Incubate for ten days at room temperature. 
Lohnis’ Method. One gm. of cheese taken under aseptic conditions 
and weighed according to the method described in another place is 
ground in a sterile mortar with 10 ¢.c. of sterile tap water, and some 
sterile quartz sand or glass powder added if necessary. The mixture is 
put into a dry, sterile 1000 c.c. flask, which is then filled to the mark with 
sterile water. After continuous shaking for several minutes, further 
dilutions with 9 ¢.c. of water are made in test tubes. Usually dilutions 
of 1 to 10,000 to 1 to 100,000 are sufficient. This is plated out in plain 
agar and gelatin. Cultures for anaerobic incubation should also be 
made. 
Harrison’s Method. Remove a plug of cheese with a sterile cork 
barer and transfer to a sterile mortar. Triturate this with sterile water 
of bouillon. This is injected to a 500 gm. guinea pig. A hole is made 
in the skin with a large needle. Through this by means of a pipette the 
cheese emulsion is blown in. Animals should be kept under observa- 
tion and immediately after death should be examined. Smears should 
be made from the diseased organs and stained from the Ziel Nielson 
method. 
Determination of Tubercle Bacilli in Cheese. (Mohler’s et al. 
Method.) Rub portions of the cheese in a mortar with physiological 
salt solution. After grinding strain the liquid through a layer of absorb- 
ent cotton and the equivalent of 2 gms. of cheese should be injected 
beneath the skin of each guinea pig. Also feed portions of the cheese 
to other pigs and keep for observations. 
FERMENTED MILKS 
These are milks in which the lactose has been changed to lactic 
acid, alcohol or carbon dioxide by the action of fungi. An extensive 
literature of the subject, together with a discussion has been prepared by 
Rogers (1916). 
