STRUCTURE AND PHYSIOLOGY OF ANIMALS 



25 



occur together in spaces scattered through the matrix : sometimes 

 condensation of the matrix round each of the spaces in Avhich the 

 cells are contained forms a cell-capsule. The outer surface is 

 covered over by a fibrous membrane the perichondrium. Carti- 



FIG. 12. Fatty tissue ; F, fat cells ; B, connective-tissue fibrils. (From Lang. ::ftcr Hanvicr.) 



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

 of lime and is then known as calcified cartila</<\ 



In lone or osseous connective tissue (Fig. 15) the matrix is exceed- 

 ingly dense and hard owing to its being strongly impregnated with 

 carbonate and phosphate of lime. It consists of numerous thin 

 plates or lamella?, which are arranged partly parallel with the sur- 

 face, partly concentrically around certain canals (c) the Naccrsian 



Fie. 1:5. Hyaline rartilage. 



Fie. 1-1. Fil>ro-f;:v:;' 



canals in which blood vessels lie. The cells, or bone-corpuscles, lie 

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

 of exceedingly fine channels the canalicida: 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 



