SECT. I4O.] 



THE TEETH. 



299 



Fig. 127. 



way n Lated to the cells from which the lacuna are formed. In 

 young teeth, Haversian canals do not occur in the normally thick 

 cement ; they are, however, quite common in old teeth, particularly 

 in the molars and in hyperostoses of the teeth. They penetrate 

 from without into the cement, ramify two to three times, and 

 then terminate in blind extremities. Their width is too small 

 (o - oo3'" to croi"') to contain marrow in addition to the blood- 

 vessels, and they are usually surrounded by some concentric 

 lamellae, as in the bones. 



Besides the above spaces, the 

 cement occasionally contains other 

 peculiar sinuous cavities, which are 

 certainly of a pathological nature 

 (see my Micr. Anat, ii. 2, p. 82, 

 fig. 202) ; frequently also canals 

 like dentinal canals (fig. 127), 

 which are sometimes close toge- 

 ther, sometimes more isolated, 

 occasionally with branches, which 

 are frequently connected with the 



terminations of the dentinal Canals Cement and dentine of the fang of an old 



1 ., c . , 7 human tooth, a. dental cavity ; b. dentine; 



and the processes Ot the lacunas. c. cement with lacuna ; e. Haversian canals. 



§ 1 40. The soft parts of the teeth comprehend the 'periosteum 

 of the alveoli, the tooth-pulp, and the gums. The periosteum of 

 the alveoli is very accurately applied to the surface of the fangs, 

 and agrees in structure with the periosteum of other parts, except 

 that it is softer, and contains no elastic elements, but rich plexuses 

 of nerves having numerous thick nerve-tubes. 



The tooth-pulp, pulpa dentis, or the fcetal tooth-papilla, which 

 has been reduced in size in the development of the tooth, rises at 

 the bottom of the socket from the alveolar periosteum, penetrates 

 into the fangs, and completely fills the cavity within them and 

 the crown, as a solid but soft, reddish substance, which is rich in 

 vessels and nerves, and everywhere intimately adherent to the 

 inner surface of the dentine. The tissue of the pulp, in so far as 

 it contains vessels, is an indistinctly fibrous connective tissue with 

 very numerous round or elongated nuclei interspersed. On its 

 surface, and seated under a delicate structureless membrane, there 

 is a lavi r 0'02'", 0'03'" to o - 04'" thick, which consists of several 

 rows of cylindrical or conical nucleated cells, o - oi2'" long, 0-002'" 

 i" 0"003'" broad, disposed perpendicularly upon the surface of 



