6 STRUCTURE AND FORMATION OF BONE. 
2. Elastic Cartilage known also as _ yellow, 
reticular, or spongy cartilage, is opaque and more 
flexible than either hyaline or fibro-cartilage. The 
ground substance is traversed by a dense branched 
network of elastic fibres, with small spaces around 
the cells. Between the meshes of these fibres, and 
in the space surrounding the cells, hyaline cartilage 
is present. Elastic cartilage occurs in the epiglottis, 
Eustachian tube, larynx, and ear. 
White-fibro cartilage is much more flexible, 
and tougher than hyaline cartilage. It consists of 
series of bundles of fibres arranged in layers, in 
which there are irregularly distributed cartilage 
cells. Where the fibres are very dense, these cells 
become very flattened. White fibro-cartilage occurs 
in the intervertebral and interarticular discs, sesamoid 
cartilages, &c. 
Development of Cartilage.—Like the rest of 
the skeletal tissues of the body, cartilage arises from 
the mesoblast. In the embryo, certain cells of the 
mesoblast assume a definite shape, usually polygonal ; 
and a transparent substance surrounds each cell, which 
‘ultimately forms the capsule. In this stage there is no 
matrix, Water the cells enlarce and: divide;andvan 
intermediate matrix is formed. On the division of a 
cartilage cell, a new capsule is formed around the new 
cells; the old capsule blending with, and ultimately 
forming part of the matrix. The process of division 
