Hammond states, that there is evidence that the connective tissues go on growing longer than other tissues in the body, and that maturity in them is not reached so soon as in other tissues. This may be one explanation of why meat from older animals is in general tougher than meat from younger animals. Hammond says that with increased feeding fat is deposited in the connective tissue.

Kinds of connective tissue. The connective tissue of meat is composed of two kinds, the yellow and the white. The amount and kind vary in meat from different animals and in different cuts from the same animal. Burns states that the function of the tissue governs the form produced. When binding power alone is required the white tissue is formed, but when elasticity as well as strength is necessary, there the yellow tissue is found. Tendons are composed almost entirely of the white, non-elastic tissue; ligaments are principally the yellow tissue. Many muscles seem to require both elastic and binding tissue, hence both are often found in the connective tissue binding the fibers.

The yellow connective tissue is feebly but perfectly elastic and is found in ligaments, in the connective tissue between the muscle fibers, in the walls of the blood vessels, and in other parts of the body. The best example of the yellow tissue is the ligamentum nuchae of the ox. It is the tough yellow ligament found along the backbone, which is used in elevating the head of the animal; it is much thicker and heavier along the ribs and fore quarter than along the loin.

The white connective tissue is non-elastic and is found in the connective tissue between the muscle fibers and in the tendons, the tendon Achilles being a good example.

Composition of connective tissue. The percentage of water in the connective tissue of the young animal is higher than in the older animal. Buerger and Gies have reported that the white connective tissue of the calf contains about 68 per cent of water, whereas that of the ox has about 63 per cent. The solids of the connective tissue are made up of inorganic and organic matter. Buerger and Gies have reported the following composition of the tendon Achilles of the ox; Vandergrift and Gies have reported the composition of ligamentum nuchae of the ox.

The collagen and elastin content of connective tissue are of especial interest in meat cookery, for both are found in the connective tissue between the muscle fibers, but heat and moisture affect the two differently.

Table 24 Composition of the Fresh Tissue of Achilles Tendon and the Fresh