A474 J. 1. WILSON: AND. J. P, HELL. 
tically shortened, the horizontal section thus cutting it obliquely. 
The hinder part of this obliquely cut portion of the lamina, as 
shown in fig. 22, does to some extent coincide with the anterior 
part of the first premolar swelling in fig. 21. It constitutes, 
indeed, as coronal sections prove, the lingual portion of the 
latter mass. The labial bulging of the Anlage is lower down, 
and is not cut through at this level (cf. fig. 21). 
The interval between the tapering ends of the Anlagen of 
the first and second premolars is a comparatively short one. 
Here the dental lamina, although quite continuous, appears 
low and relatively insignificant.1_ This is especially interesting, 
as it is just here that one might expect some trace of Thomas’s 
hypothetical ‘ pm2.” 
A glance at fig. 21 is sufficient to show how far forward the 
anterior tapering end of the second premolar enlargement of 
the lamina extends. This enlargement is, indeed, of very 
considerable antero-posterior extent. Anteriorly its cross- 
section is rounded, but posteriorly it is much more vertically 
extended, gradually narrowing at the same time, to be con- 
tinued on as the vertically elongated but otherwise unmodified 
lamina, which is found in the region between the second and 
third premolars (cf. text Fig. 1, a—e). 
Fig. 22, representing a horizontal section taken at a higher 
level than fig. 21, shows the higher hindmost portion of p2 
cut somewhat obliquely, and gradually passing back into con- 
tinuity with the freed dental lamina on the lingual side of the 
well-developed milk premolar, dp. 
On the labial side of the basal margin or “neck” of the 
1 The lamina looks lower than it really is because it is somewhat folded in 
its length, so that in cross-section the long axis (being attached to free 
margin) is not straight, but crooked. Such bending of the lamina near the 
neck is a common enough phenomenon, and here it is strongly marked. An 
outwardly projecting elbow in cross-section thus produced may easily enough 
be mistaken for a true outgrowth of cells in some cases, and such an error 
must be carefully guarded against. The separation of the lamina from the 
oral epithelium frequently leaves such an elbow projecting freely, and this 
may form another source of error in interpretation, 
