Stock, whether made from fresh meat, or from odds and ends, solidifies when it becomes cold, if it contains a goodly amount of gelatine. This constituent of meat, in the flesh, tendons and bones of young animals, is more soluble than it is in those of more mature age. It is found largely in the bones and tendons, but there is also a considerable quantity in the connective tissues of the lean meat. It takes, moreover, a higher degree of heat to extract gelatine from meat than some other constituents. A bouillon, therefore, made entirely of lean meat, will jelly or become solid, if there be taken a pound of meat to a pint of water and the juices be extracted at a temperature between 180° and 200° Fahr.

Stock that jellies may be kept longer than that in a liquid state, as the air does not penetrate it readily. This is the case, more especially, if the stock be strained into bowls of a size convenient for future use and the covering of fat be kept intact. The addition of vegetables is not desirable, if the stock is to be kept, for the juices of vegetables sour more quickly than the juices of meat.