13 
calves’ stomachs, the casein, which in fresh milk is contained 
ir. what is termed colloidal condition, changes its nature. It 
coagulates, ‘thickens or curdles, as every housewife knows. 
This takes place sooner when milk is heated. These are points 
of extreme importance in the making of condensed and espe- 
cially evaporated milk and also milk powder, all of which pro- 
cesses attempt to change the milk solids as. little as possible. 
In proportion to the concentration of milk, naturally the acid: 
content is increased, and the curdling occurs so much sconer. 
But there are great differences even in fresh milk as 
drawn from the udder, not only as to the proportional varia- 
tions of its constituents (as shown in the above figures) but 
also as to its behaviour in regard to coagulation. The careful 
cheesemaker knows that there are differences as to the kind 
of cows, the season of the year, the weather, the locality, the 
feed and general care of milk herds, ete. He adjusts his 
methods accordingly, in the amount of rennet used and tem- 
peratures applied for “setting” his milk and treating the curd. 
At closer inspection we find that there are considerable varia- 
tions in the coagulability of milk between individual cows, in 
the same stable and fed on the same feed. Many of the fac- 
tors are uncontrollable, and are not yet fully explained by 
science.* 
These preliminary remarks have been made to indicate 
that the first technical essential in the manufacture of all these 
products is a first-class milk from healthy, well-tended and 
well-fed cows, and that the milk must enter into the process in 
*The writer may suggest from experience a simple and practical 
test which might prove useful to stable inspectors especially in evapo- 
rated milk districts to detect cows that secrete milk of abnormal coagu- 
lation: Adjust a rennet solution to such a strength that a teaspoonful 
will coagulate a water glass about % full of milk just as drawn from 
the udder in about 30 seconds. After about another 30 seconds the 
coagulum should be firm and smooth. If the content of the glass is 
turned over on the palm of the hand it should stand like a nice jelly 
pudding. If broken with the finger a clear greenish whey should run 
off from it. Abnormal milk will be readily detected by the time it re- 
quires for thickening, by a less firm, flaky or stringy coagulum or a 
whitish troubled whey. It may be remarked that differences are fre- 
quently found: between the milk of individual teats of the same cow. Axy 
kind of affection, even the slightest inflammation, careless milking, etc., 
will affect the milk in this respect. After udder diseases are apparently 
healed it may still take months before a normal milk is secreted again. 
