306 MICROSCOPIC ANATOMY OF THE TEETH 



Near the end of the root they are chiefly oblique, passing 

 upwards and outwards to their attachment to the bone, but 

 are crossed by bundles of fibres passing in the opposite 

 direction and interlacing with them. It is thus seen that 

 there is no separate membrane connected with the tooth 

 and another with the alveolus, but its fibres are continuous 

 from one side to the other, although they are coarser on the 

 outer side of the membrane and finer on the side of the 

 cement ; but there is no distinct arrangement in layers, 



FIG. 199. Periodontal membrane showing oblique direction 

 of fibres and their intercrossing. ( x 450.) 



the finer fibres passing insensibly into the coarser ones. 

 The oblique direction of the fibres and their intercrossing 

 with others passing in an opposite direction are well shown 

 in fig. 199. 



The general arrangement of the fibres is such as to swing 

 or suspend the tooth within the socket and allow of a certain 

 amount of movement, preventing undue pressure on the 

 nerves and blood-vessels of the alveolus. 



Blood-vessels are abundant in the periodontal membrane 

 midway between the bone and the tooth, and numerous 

 capillaries are seen near the cement, and it is richly 

 supplied with nerves. 



