MODIFIED MILK AND MILK PRODUCTS lip 



they found that infected cheese 220 days old set up, when 

 inoculated, marked generalized tuberculosis, and when 261 days 

 old slight tubercular lesions. 



To examine cheese for tubercle bacilli the method of Mohler, 

 Washburn and Doane may be used. Portions of the central 

 part of the cheese are rubbed up in a mortar with sterile normal 

 saline solution. After being well ground the liquid is strained 

 through a layer of absorbent cotton and the equivalent of 

 2 grm. of cheese injected into each guinea-pig. 



VI. Ice-cream. 



The term ice-cream covers articles which are to some extent 

 prepared differently and which contain different constituents, but 

 these differences of composition are not extensive as regards 

 ice-creams made in this country. 



In its simplest form ice-cream consists of milk and sugar, 

 with a thickening agent such as corn-flour and with or without 

 eggs. Flavouring agents and sometimes colouring matters are 

 added, while gelatine is sometimes used in the manufacture. 



Cream, as such and apart from milk, does not appear to be 

 used in the preparation of the article vended in this country as 

 " ice-cream." While the mixture is always heated the duration 

 of the heating varies greatly, and frequently some constituents 

 are added afterwards. The mixture is cooled and subsequently 

 frozen. 



From the bacteriological point of view the chief points of 

 importance are that the constituents form a food highly nutrient 

 for bacteria, that it is often made from materials already heavily 

 infected with bacteria, that this food is heated but not sterilized, 

 that the cooling is natural and therefore prolonged, and that the 

 subsequent freezing has no inhibitory action upon any of the 

 harmful bacteria which it may contain. 



Bacterial content. 



Buchan found that the average period of cooling before freez- 

 ing was about 2o| hours. From numerous reports by Medical 

 Officers of Health it is evident that both the preparation 



