50 ELEMENTS OF HISTOLOGY. [Chap. VH. 



another. The final stage is reached when the ground 

 substance is permeated by a dense network of elastic 

 fibrils (Fig. 32), so arranged that spherical or oblong 

 spaces are left, each of which contains one or two 

 cartilage cells, surrounded by a smaller or larger zone 

 of hyaline ground substance. 



CHAPTER VIL 



BONE. 



62. BONE, as osseons substance, is associated with 

 several other soft tissues to form a bone in the ana- 

 tomical sense of the word. 



(a) The periosteum. Except at the articular 

 surfaces, and where bones are joined with one another 

 by ligaments or cartilage, all bones are covered with a 

 vascular membrane of fibrous connective tissua This 

 is the periosteum. It consists in most instances of 

 an outer fibrous layer, composed of bundles of fibrous 

 tissue densely aggregated, and an inner, or osteogenetic 

 layer, which is of loose texture, consisting of a mesh- 

 work of thin bundles of Jibrous tissue, in which nu- 

 merous blood-vessels and many protoplasmic cells are 

 contained. The blood-vessels form by their capillaries 

 a network. The cells are spheroidal or oblong, each 

 with one spherical or oval nucleus. They have to 

 form bone-substance, and are therefore called the osteo- 

 blasts (Gegenbaur). 



(b) The cartilage is hyaline cartilage, and its 

 distribution on and connection with bone have been 

 mentioned above on pp. 46 and 48. 



63. (c) The marrow of bone is a soft vascular 

 tissue, filling up all spaces and cavities. It consists 



