Xl] ELASTIC CARTILAGE. BONE. TEETH 83 



largely of a close meshwork of fibres, leaving a hyaline 

 portion (stained blue in a) immediately around the 

 cells. In places, the elastic substance may take the 

 form of thick nodular bars. 



Externally, areolar tissue ; note the transition of the 

 elastic cartilage into this by the elongation of the cells, 

 the disappearance of the capsules, and the substitution 

 of white fibrous tissue for most of the elastic fibres. 



The elastic fibres are best shown in b, the cells and 

 their hyaline capsules in a. 



A section may also be stained in picrocarmine for an hour or 

 more, and another in hoematoxylin and picric acid, and the two 

 mounted in glycerine. In the former the perichondrium is 

 stained red arid shows well the passage of this to the cartilage, 

 in the latter hyaline cartilage is stained blue and the elastic 

 fibres deep yellow. 



Cartilage is apt to buckle when dehydrated so that it 

 is generally best to mount it in glycerine. 



4. Structure of Bone. Transverse section through 

 the shaft of an adult long bone. (The bone is dried ; thin 

 pieces are cut with a saw, ground down and mounted in 

 balsam.) a. Examine under a low power. Most of the 

 smaller spaces (i.e. Haversian canals, lacunae, canaliculi) 

 will be filled with air or debris and will therefore appear 

 dark. Observe 



The central medullary cavity surrounded by bony 

 substance. 



At the circumference, the circumferential lamellae 

 running parallel with the surface; inside this the 

 Haversian systems, each consisting of a Haversian 

 canal surrounded by concentric lamellaB which are 



62 



