32 ON THE ORIGIN AND DEVELOPMENT OF THE 



human shape. The molar pulps begin to be perforated also 

 by three canals, which, proceeding from the surface to their 

 centres, gradually divide their primary base into three second- 

 ary bases, which become developed into the fangs of the future 

 teeth. While this is going on, the sacs grow more rapidly 

 than the pulps, so that there speedily exists an intervening 

 space in which is deposited a gelatinous granular substance, 

 at first in small quantity, and adherent only to the proximal 

 surfaces of the sacs ; but ultimately, about the fifth month, 

 closely and intimately attached to the whole interior of these 

 organs, except for a small space of equal breadth, all round the 

 base of the pulp, which space retains the original grey colour 

 of the inner membrane of the follicle ; and as the primary base 

 of the pulp becomes perforated by the canals formerly men- 

 tioned, the granular matter sends processes into them, which, 

 adhering to the sac, reserve the narrow space described above 

 between themselves and the secondary bases. These processes 

 of granular matter do not meet across the canals, but dis- 

 appear near their point of junction. The granular matter is 

 closely applied, but does not adhere to the surface of the pulp. 

 " Whatever eminences or cavities the one has, the other has 

 the same, but reversed, so that they are moulded exactly to 

 each other." 



Each branch of the dental artery, as it arrives at the fundus 

 of its destined sac, sends off a number of radiating twigs, which 

 run in the substance of the cellular submucous tissue (which 

 constitutes the outer membrane of the sac) towards the gum, 

 from which others proceed to inosculate with them. The 



on the subject appear to have been derived from the examination of jaws in 

 which the lips and walls of the secondary dental groove "gencive passagere," 

 had not become completely adherent or obliterated. In this way the indistinct 

 mouths of the milk-tooth sacs on the floor of the groove "gencive permanent," 

 did not escape the notice of this most accurate observer. The cartilages of the 

 gum described by Serres (Essai, p. 10) are to be considered as the walls of the 

 groove in the semicartilaginous condition which they assume after closure. 



