90 BOARD OF AGRICULTURE. 



means of acid, as many have taught. Be the explanation of the 

 action of rennet what it may, we must, until better advised, be 

 content to accept and act upon the facts as demonstrated by ex- 

 perience, the most important of which are, first, that rennet curdles 

 milk irrespective of acid ; and secondly, that the presence of lactic 

 acid (from the conversion of milk sugar) facilitates coagulation. 



Cheese is often made wholly of new milk, but in such case the 

 separation of the whey is more difficult, and the product somewhat 

 inferior to that made of milk in which the conversion of sugar into 

 lactic acid has made some progress. Various attempts have been 

 made to measure the degree of acidity, and several acidimeters 

 have been proposed, but none so far as I am aware have been suc- 

 cessfully introduced into practice. It is found by experience that 

 if the night's milk be kept at or below 62° until morning, a 

 little sour whey, one day old, may be added to advantage, say a 

 quart to thirty gallons of milk ; but if the temperature of the 

 evening's milk in the morning be 65° or upwards, there is no need 

 of sour whey being added, because lactic acid is already present 

 in sufficient quantity. 



Milk is subject to many and curious changes, the peculiar nature 

 and causes of which are little understood. Some of these are evi- 

 dently the provisions of Nature for special purposes. The first 

 milk, or beastings, as it is sometimes called, is very unlike that 

 secreted at a later period, both in its chemical composition and in 

 its eflects. It is specially adapted to the wants of the calf immedi- 

 ately after birth, and should never be withheld from it. The milk 

 secreted by cows during the season of sexual heat is quite unlike 

 that of other times. Persons in robust health may sometimes par- 

 take of it without serious injury, but it should never be given to 

 infants. By a wise provision cows are not subject to this condition 

 while suckling their offspring, and what is dangerous to a calf 

 should be cautiously withheld from a delicate infant, or person in 

 feeble health. Such milk is unfit for dairy use as well as for direct 

 use for food. Mr. Willard, in reply to an inquiry on this point, 

 writes me as follows : " The milk of cows in heat does sometimes 

 play queer pranks with cheese. You will remember I suggested 

 this to be the cause of the trouble in the three cheeses which we 

 saw at Frazce's factory, made from one vat of milk which Mr. F. 

 said could not be properly cooked. I have had it occur in my own 

 dairy, when several cows were in heat at the same time, when the 



