454 J. T. WILSON AND J. P. HILL. 
most important and striking feature present. This consists in 
the differentiation, towards its anterior end, of a shallow but 
quite definite mesodermal papilla, which indents its labial side, 
forming the rudiment of the true milk predecessor of the per- 
manent third incisor, whose Anlage forms the bulk of the 
swelling. 
The series of drawings (figs. 1—5) completely illustrates the 
characters of this milk rudiment (di) and its relations to 
the swollen portion of the dental lamina representing the 
Anlage of the permanent tooth (¢3). 
Thus fig. 1 shows the lamina (dl.) in advance of the 73 
region destitute of any differentiation. In the next succeeding 
section, fig. 2, the labial outgrowth (d23) has appeared very 
abruptly growing out from the “ neck” of the lamina. In the 
following section (fig. 3) the milk enamel-organ (di3) is 
broader, and its relation to the lamina is slightly modified. 
The connective tissue on its labial aspect promises to form a 
papilla (mp.), and there is a slight tendency to cupping of the 
enamel-organ itself. As yet the main portion of the dental 
lamina exhibits very little modification, but from this point 
backwards it swells considerably, so that in fig. 4, three sec- 
tions further back, it is decidedly more massive, whilst at the 
same time its differentiation from the milk enamel-organ is 
hardly visible, being indicated only by the arrangement of the 
nuclei of the constituent cells. Still the milk papilla (mp. di 2) 
is distinct though very shallow. Three sections still further 
back (fig. 5) the milk enamel-organ has wholly disappeared, 
leaving, however, a much-thickened dental lamina, representing 
the hinder and main portion of the Anlage of the permanent 
third incisor (72). 
The precise position of the milk-tooth rudiment on the 
antero-lateral aspect of the entire third incisor Anlage is defi- 
nitely established, not merely by an examination of the serial 
sections figured, but by comparative study of sagittal series, 
which affords complete corroboration of the statements just 
made. 
It will be shown in connection with the description of the 
