358 THE DAIRYMAIS'S MANUAL. 



been used, besides sour milk, and the common rennet, 

 to produce the curd. 



Caseine itself is an acid substance and combines with 

 the soda of the milk under certain circumstances, and 

 then becomes soluble in the water of the milk, althougli 

 it IS practically insoluble in pure water. When any acid 

 is added to the milk it takes the soda from the caseine 

 and combines wath it, thus causing the caseine to re- 

 sume its insoluble condition and separate from the fluid. 

 The action of rennet differs in some degree from this, 

 but it is quite as simple and easy to understand. This 

 substance is the digestive or fourth stomach of a young 

 calf, cured and preserved for keeping and use. The 

 stomach in its fresh state always contains a quantity of 

 curd in it which is sometimes washed out, together with 

 some mucus, which is almost always found with it in 

 the stomach. In some localities this curdy matter is 

 satted. for immediate use; in others it is left in the 

 stomach and both are salted together, and it is not 

 unusual to feed the calf a short time before it is killed, 

 so as to procure a large quantity of this curd. 



The mode of salting varies. Sometimes the stomach 

 is partly filled with salt and some is applied to the out- 

 side, and the stomach is then rolled and hung in a warm 

 place to dry. Other dairymen pickle the stomachs iii 

 brine for a few days, and then dry them; this pickle is 

 then preserved for use as rennet. In Cheshire, Eng- 

 land, the stomachs are packed in jars in layers with salt 

 inside and outside of them, and kept for a year; in some 

 European countries the stomachs are chopped finely, 

 mixed with salt and crumbs of bread into a paste, and 

 preserved in bladders 'for nse. In Italy, where the famous 

 Parmesan cheese is made, the stomachs are chopped up 

 and made into a paste, with salt, pepper, and whey, and 

 this paste is dried for use. 



The common practice is to keep these various prepara- 



