Elementary text-book of zoology, tr Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote elementarytextbo01clau Year: 1892-1893 40 GENERAL PART. elastic cartilage; the latter containing a network of elastic fibres. There are also intermediate forms, approximating to the fibrillar connective tissue, in which cartilage cells may be surrounded by bundles of connective tissue fibres. The cells are placed in spaces, which are usually round, in the intercellular substance, and are sur- rounded by firm layers which are separated off from the latter, a
Elementary text-book of zoology, tr Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote elementarytextbo01clau Year: 1892-1893 40 GENERAL PART. elastic cartilage; the latter containing a network of elastic fibres. There are also intermediate forms, approximating to the fibrillar connective tissue, in which cartilage cells may be surrounded by bundles of connective tissue fibres. The cells are placed in spaces, which are usually round, in the intercellular substance, and are sur- rounded by firm layers which are separated off from the latter, and have the appearance of capsules. These so-called cartilage capsules were formerly looked upon as the membranes of the cartilage cells, analogous to the cellulose capsules of plant cells; a view of them which is not in any way opposed by what is known as to their development as secretions of the protoplasm. Nevertheless, the capsules stand in closer relation to the earlier formed intercellular substance which has been produced in the same way, in that they often fuse with it. The growth of the cartilage is accordingly in the main interstitial. We frequently see in the spaces in the cartilage several generations of cells surrounded by special capsules placed one within the other. In such cases the secreted cap- sules have remained separate from the intercellular sub- stance. Certain kinds of car- tilage, moreover, have spindle- shaped cells, and sometimes the cells are prolonged into numerous radiating processes. Calcareous salts may also be deposited in the intercellular substance in a greater or less quantity. In this way arises the so-called in- crusted cartilnge, or the cartilage bone (fig. 30), which in the sharks is present as a persistent form of skeletal tissue, but in the higher vertebrates only as a transitional structure. Cartilage owes its special usefulness as a skeletal tissue to its rigidity. It is sometimes found in the Invertebrata (Cephalopoda, tubicolous wor
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