114 THE PERMANENT TEETff. 



at the inner side of those of the deciduous teeth, to the sac of 

 which they are attached at top by a neck-like process, as seen 

 in Fig. 25. As the infantile teeth rise up and make their way 



Fig. 25. 



through the gum, this process becomes connected with the 

 gum, and forms what is called by Hunter the gubernaculum^. 

 dentis, from its influence in giving the permanent teeth their 

 proper vertical direction, and preventing their making their 

 way at random through the sides, as they do occasionally in 

 cases where the gubernaculum has been destroyed. 

 Delabarre has given the gubernaculum the name of iter 

 dentis, from an erroneous belief that it was tubular, like the 

 duct of a sebaceous follicle, and gradually opened as the tooth 

 progressed. 



At the fifth month of foetal life, according to Bell, and the 

 eighth and ninth, according to Blake and Fox, the germs of the 

 first permanent molars, may be seen at the outside of the in- 

 fantile row, and those of the permanent incisors behind the 

 deciduous. Fig. 25 1, 2, shows the attachment of the incisor 

 and molar germs of the two sets, just prior to the eruption of 

 the first. The permanent germ is at first placed in the socket 

 of the deciduous tooth, of which it appears, on first view, to 

 be an offshot or gemmiperous production. Its vessels and 

 nerves are believed to be mere branches of those of the deci- 

 duous set. By degrees a distinct socket is formed for it be- 

 hind the latter, and its process or gubernaculum is elongated, 

 as seen in Fig. 25 3. When the deciduous teeth have cut the 

 gum, the two sockets are completely distinct, as seen in Fig. 

 26, and the gubernaculum is attached to the gum. 

 Ossification first commences in the permanent set on the 

 anterior molares, and may be seen at birth ; at the age of 



