Fortunately, in course of time, the useful ferments establish themselves in large quantities in the dairy; they impregnate the air of the factory, and cling to the vessels and the clothing of the operatives. From the moment the milk is drawn, it becomes exposed to the influence of these germs, which, developing rapidly in the warm milk, and becoming entangled in the curd when the rennet is added, accompany it through the operations that follow. On the Continent it appears common to curdle the milk at a much higher temperature than we do. Duclaux speaks of the rennet being frequently added just as the milk comes from the cow; and if it has been allowed to cool, it is warmed up to the natural temperature, 95°-98° F. In making fine cheeses but little rennet is used, and the coagulation takes a long time. The curd is soft and full of whey, which is drained off slowly and as completely as possible, in order to get rid of the milk sugar. That which is left is chiefly converted into lactic acid, which renders the new cheese slightly acid. Soon, however, the casein ferments begin to develop over the surface of the cheese, giving rise to carbonate of ammonia, which neutralises the acid, and leaves the cheese in the end slightly alkaline. From the living cells of the ferment are at the same time secreted a diastase similar to the active principle which in malt, and in all germinating seeds, converts the starch into sugar. This penetrates the curd little by little, and renders it soluble, and thus a yellow translucent layer creeps gradually inward to the centre, and replaces the white and opaque casein. When isolated, this diastase attacked curd so strongly as to reduce it in 3 or 4 days to the consistency and appearance of Camembert cheese; but, as the flavouring organisms were absent, the resulting product was insipid and tasteless. This action resembles strongly the digestion to which the cheese is afterwards more completely subjected in the body. Indeed, the similarity in properties between this peculiar principle and the ferment of the pancreas is very marked. Simultaneously with the digestive diastase there is also secreted a diastase capable of coagulating the casein; but the cheese maker does not wait for this to be developed, but adds to the milk some rennet, which is a solution containing this diastase in considerable quantity. Such, in short, is the rationale of cheese curing--first, an organised ferment decomposes the curd, and produces in small quantities highly flavoured compounds, which, like a condiment, give relish to the whole mass; and secondly, a diastase, or unorganised ferment secreted by the organism, mellows the curd and renders it more easily soluble.