PULPS AND SACS OF THE HUMAN TEETH. 25 



Upon examining the two incisive teeth which had cut the 

 gum, it was found that a bristle could be inserted between 

 their surfaces and the gum for one-third of an inch. Through 

 the soft parts a transverse section was made, which was after- 

 wards continued through the jaw and one of the teeth by 

 means of a very fine saw. 



It was now observed that the tooth (#, Fig. 24, y) had 

 acquired nearly two-thirds of its fang, and that the sac had 

 again become an open follicle (&). This follicle was shorter 

 than the whole length of the tooth by the length of the pro- 

 truding portion of the latter. At the mouth of the follicle, its 

 lining membrane was continuous with the surface of the gums, 

 and continued free till it arrived at the termination of the 

 enamel, where it united to the surface of the fang of the tooth, 

 but could be separated from it as a continuous membrane, and 

 at the lower end of the root it became continuous with the 

 surface of the pulp, whose base was yet considerable. Upon 

 removing the bone in front of the neighbouring lateral tooth, 

 which had not yet passed through the gum, it was observed 

 that the extremity of its fang, or rather the fundus of its sac, 

 was deeper in the jaw than that of the central by a length 

 equal to the protruding portion of the latter. This change of 

 level had not, however, taken place in the case of the alveoli, 

 that of the central being rather deeper than the lateral. The 

 space intervening between the bottom of the alveolus of the 

 central tooth and the fundus of its sac was occupied by a 

 spongy filamentous tissue, through which the dental vessels 

 and nerves proceeded. 



14. The lower jaw of an infant, which had cut all its 

 milk-teeth, and which was probably between four and five 

 years old, was prepared in the same manner as the last. 



The sac of the anterior permanent molar (6, Fig. 25) was 

 situated under the gum in front of the coronoid process, and a 



