28 



ZOOLOGY 



SECT. 



of masses of large cells in which the protoplasm has more or less 

 completely become replaced by fat, the cells being bound together 

 into groups and masses or lobules by means of fibrous connective 



tissue. 

 In the case of cartilage the matrix is of a firm but elastic 



character, sometimes quite homogeneous in appearance (hyaline 



cartilage, Fig. 16), sometimes 

 permeated by systems of 

 fibres (fibro-cartilage, Fig. 

 17), which may be of an 

 elastic nature (yellow elastic 

 cartilage). The cells are 

 usually rounded, and as a 

 rule several occur together 

 in spaces scattered through 

 the matrix ; sometimes 

 condensation of the matrix 



round each of the spaces 

 in which the cells are con- 

 tained forms a cell-capsule. 

 The outer surface is 

 covered over by a fibrous membrane the perichondrium. Carti- 

 lage is frequently hardened by the deposition in the matrix of salts 

 of lime, and is then known as calcified cartilage. 



In bone or osseous connective tissue (Fig. 18) the matrix is exceed- 

 ingly dense and hard owing to its being strongly impregnated with 

 carbonate and phosphate of lime. It consists typically of numer- 

 ous thin lamellae, which are arranged partly parallel with the sur- 

 face, partly concentrically around certain canals the Haversian 



FIG. 15. Fatty tissue. F, fat-cells ; B, connective- 

 tissue fibrils. (From Lang, after Ranvier.) 



Flo. 10. Hyaline cartilage. 



FIG. 17. Fibro-cartilage. 



canals (c) which contain blood-vessels. The cells, or bone-corpuscles, 

 lie in minute spaces the lacuna between the lamellae, and a system 

 of exceedingly fine channels the canaliculi extend from lacuna 

 to lacuna, containing fine protoplasmic processes by means of which 

 neighbouring cells are placed in communication with one another. 

 The outer surface of the bone is covered by a vascular fibrous 



