One of the most important processes in the manufacture of good cheese is the preparation of the rennet. This is made of the inner lining or mucous membrane of the stomach of the young sucking calf, sometimes called the bag or maw; and the use of it was undoubtedly suggested, originally, by observing the complete and rapid coägulation or curdling of milk in the stomach of a calf newly killed. “Coägulation is the first process of digestion in the fourth stomach of the calf. There are numerous glands scattered in and about the stomach that secrete a fluid which readily and almost immediately accomplishes this coägulation. They are always full of it; even after the animal is dead they remain filled with it; and if the stomach is preserved from putrefaction, this fluid retains its coägulating quality for a considerable period; therefore dairy-women usually take care of the maw or stomach of the calf; and preserve it by salting it, and then, by steeping it, or portions of it, in warm water, they prepare what they call a rennet. After the maw has been salted a certain time, it may be taken out and dried, and then it will retain the same property for an indefinite period. A small piece of the maw thus dried is steeped over night in a few teaspoonfuls of warm water, and this water will _turn_ the milk of three or four cows.” It is important that rennet enough should be prepared at once for the whole season, in order to secure as great a uniformity in strength as possible. The object should be to produce a prompt, complete, and firm or compact coägulation of all the cheesy matter. Mr. Aiton, in his admirable treatise on the Dairy Husbandry of Scotland, gives the simple method of preparing the rennet in the dairy districts, as follows: “When the stomach or bag--usually termed the yirning--is taken from the calf’s body, its contents are examined, and if any straw or other food is found among the curdled milk, such impurity is carefully removed; but all the curdled milk found in the bag is carefully preserved, and no part of the chyle is washed out. A considerable quantity of salt--at least two handfuls--is put into and outside the bag, which is then rolled up and hung near a fire to dry. It is always allowed to hang until it is well dried, and is understood to be improved by hanging a year or longer before being infused.