468 Jj. La WALSON AND J. P: HILL; 
The structure of the differentiating dental lamina in the 
third incisor region will be rendered further intelligible by a 
reference to fig. 19, which illustrates a coronal section through 
this region. Here again the bilobed character is only ob- 
scurely manifested, but in the next succeeding section it is as 
plainly seen as in 72 in fig. 17, and the cellular aggregation 
at the site of the future papilla is also clearly seen. The line 
ab. shows the approximate level of the horizontal section in 
fig. 18. Here the almost isolated remains of the enamel-organ 
of di3 are well shown. 
Tn this figure (19) it will be observed that the attacliment of 
the whole mass to the oral epithelium is already narrowed. 
The deep notch between oral epithelium and dental lamina on 
the lingual side represents the result of the process of pinching 
off from the oral epithelium which is now in progress. Origi- 
nally the attachment no doubt corresponded to the whole 
breadth of the base of the mass lingually. As a result of the 
pinching off, the primitive continuity of the dental lamina on 
its lingual side with the oral epithelium is now obscured. 
The plane of the horizontal section through the region of 73 
(fig. 18) is such that although it does not shave the upper free 
border of the low dental lamina between the low-lying 72 and 
72, it does cut the lamina between 72 and i4, obliquely for a 
certain distance (fig. 18 d/4). The fourth incisor Anlage 
itself, however, lies wholly at a higher level. 
It is unnecessary to enter upon a detailed description of the 
Anlagen of the fourth and fifth incisors. The following state- 
meuts will suffice. The dental lamina is continuous throughout, 
both in its own extent and with the oral epithelium. It has 
undergone enlargement at two places corresponding respec- 
tively to the fourth and fifth incisors. These localised 
enlargements are for the most part of a general character, 
though bulging mainly to the labial side, except that in each 
case there is already to be found, projecting labially from near 
the base of each rounded swelling, a somewhat attenuated 
epithelial process, precisely comparable in general appearance, 
structure, and relations to that marked ‘‘ di? ” in figs. 17 and 
