STIMCTURE AND PHYSIOLOGY OF ANIMALS 



27 



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 contained forms a cell-capsule. The outer surface 



IS 



Fio. 15.— Fatty tissue ; F, fat-cells ; B, connective-tissue fibrils. (From Lang, after Ranvier.) 



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 

 canals (c) — in which blood-vessels lie. The cells, or bone-corpuscles, lie 



Fio. 16.— Hyaline cartilage. 



Fid. 17.— Fibro-cartilage. 



in minute spaces — the lacunae — 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 



