36 



THE ESSENTIALS OF HISTOLOGY 



siderable development of elastic fibres. It occurs also in an almost 

 pure form in the walls of the air-tubes, and uniting the cartilages of 

 the larynx. It also enters largely into the formation of the walls of 

 the blood-vessels, especially the arteries. 



In the ligamentum nuchae the fibres are very large and angular 

 (fig. 38) ; they often exhibit cross-markings or even transverse clefts. 

 When dragged asunder, they break sharply across ; they constantly 

 branch and unite, so as to form a close network. In transverse 

 section they are seen to be separated into small groups (fig. 39) by 

 intervening white bundles of connective tissue. 



FIG. 39. CROSS-SECTION OF ELASTIC 

 FIBRES FROM THE UGAMENTUM 

 NUCHAE OF THE OX. 



FIG. 38. ELASTIC FIBRES FROM THE LIGA- 

 MKNTUM NUCHAE OF THE OX, SHOWING 

 TRANSVERSE MARKINGS ON THE FIBRES. 



Elastic tissue does not always take the form of fibres, but may 

 occur as membranes (as in the blood-vessels). Sometimes the fibres 

 are very small, but their microscopical and chemical characters are 

 always very well marked (see p. 31). 



Fibrous tissue is almost wholly made up of bundles of white fibres 

 running in a determinate direction. These again are collected into 

 larger bundles, which give the fibrous appearance to the tissue. The 

 bundles are constantly uniting with one another in their course, although 

 their component fibres remain perfectly distinct. 



The interspaces between the larger bundles are occupied by areolar 

 tissue (fig. 40) in which the blood-vessels and lymphatics of the fibrous 



