Fig. 440.
1. Cartilage from a mouse’s ear closely resembling vegetable tissue ×200; 2. Cartilage from rabbit’s ear, with nucleated cells embedded in matrix; 3. Cartilage from the end of a human rib ×300.
The better specimens for microscopical examination are those taken from very young animals, in whom the ossific process is still incomplete. In order to examine cellular cartilage, the ear of the mouse should be taken and just dried sufficiently to enable fine sections to be cut by the microtome transversely ([Fig. 440]).
Cartilage forms the entire skeleton of a certain number of fishes, as the skate, lamprey, ray, shark, &c., the cells of which are embedded in a matrix of granular matter, which has been properly termed intercellular. The nearest approach to ossification of cartilage in fishes is that of the cuttle-fish; in this stellate cells are freely distributed, as shown in [Fig. 441], No. 3.
Fig. 441.
1. Cartilage from the head of the skate, cells filled with nuclei; 2. Cartilage from frog, oblong cells with nuclei; 3. Cartilage from cuttle-fish, with stellate cells, × 200.
White fibro-cartilage occurs between the bodies of the vertebræ as a connecting medium. In this kind the cells are more widely distributed, specimens of which may be taken from the central portion of an interarticular disc of any animal. The oval or circular corpuscles will be seen surrounded by an abundance of fibrous tissue.
An acquaintance with the degeneration of the textures with which we have been dealing may be of service to the student, as he may, in the course of his examination, meet with an abnormal condition altogether different to those described. The process of degeneration is usually a slow one, except in the case of fatty infiltration, an example of which is furnished by the fatty degeneration of the liver in Strasburg geese. Muscular tissue is very prone to fatty degeneration, and fatty heart is often met with. Calcareous degeneration of the muscles, ligaments, and cartilages, as well as morbid deposits, are not at all uncommon in these structures. In [Plate XIX]., No. 9, a small section is given of an enchondroma, and in which the round or ovoid cells of the cartilage are seen degenerated and converted into granular masses of a calcareous nature. [Fig. 442] is a somewhat more highly magnified section of a calcareous or morbid growth, taken from a human subject in which a morbid growth was seen to be gradually destroying the bone and cartilage cells.
