1888.] 



NATURAL SCIENCES OF PHILADELPHIA. 



259 



the sides of the vault is marked by a whitish surface which yields 

 to pressure. In some individuals this motion can, be traced as far 

 forward as the first post-sutural fold. The tract is best developed 

 when the roof is normally formed. With a flat arch and a median 

 exostosis present, the track is small. With rugse well shown, but 

 broken, the place of the interruption occurs across the track. The 

 pale tracks appear to be entirely absent in high, acute arches. An 

 association of the track and the color marking of the hard palate 

 can also be detected, The high-arched palates are uniformly of a 

 red color, while the flat arches are red only along the median line 

 and at the region of the gum. A test exists here for the rate of 

 blood vessel activity of the palatine structures and, by inference, of 

 the rates of development of the maxilla. 



Figure 4, 

 The palate is normal in curvature. The incisive pad and raphe are 

 continuous. The sutural folds are entire, the left fold extending 

 farther up along the raphe than does the right. Median concresence 

 is seen on the left side. 



Variations of the Rug^. 



At the risk of repeating some of the facts of the preceding 

 description it is proposed to discuss under this head the principal 

 variations of the rugae. They will be included under the following 

 propositions : 



I. The rugse of the lett side tend to be the better developed (see 

 figs. 3, 4, 5, 6, 7, 8,). 



