268 PROCEEDINGS OF THE ACADEMY OF [1888. 



The axis of the incisive pad when deflected from that of the 

 median line is inclined toward the side which is minimized by the 

 non-appearance or extraction of one of the incisor teeth of the per- 

 manent set, by the eruption of a tooth on the buccal or labial side 

 of its arch, or by some third related cause (see fig. 3). 



In one adult subject whose palatal vault exhibited straight, reg- 

 ular, unbroken rug?e on the right side retained on the left all the 

 rugse broken and parts of two entering into the composition of the 

 pre-sutural and the sutural. Tlie left side was narrower than the 

 right. It is not likely that the irregularity of the rugse on the left 

 side was independent of the fact that the lateral incisor and the 

 second bicuspid were absent from the upper jaw, and that the sec- 

 ond bicuspid on the same side of the lower jaw was also absent, its 

 place being taken by the second milk molar which had never been 

 changed from the time of its eruption and was in all respects a 

 normal, healthy tooth. The left side of the face was slightly small- 

 er than the right. 



In a girl of twelve years the rugse were normal on the left but on 

 the right the sutural fold Avas forked and the remaining folds broken. 

 On the left side the left second bicuspid tooth was absent, while 

 on the right both teeth were in position. 



It is always of importance to remember that the mouths of chil- 

 dren in whom the deciduous canines and molars are yet in position 

 at a time when the permanent incisors and the first permanent 

 molar have been erupted, that the rugse exhibit a disposition to 

 approach one another toward these teeth. Is it possible that the 

 change from the infantile arrangement where the folds are entire, 

 regular and symmetrical to that of the older child, where the ac- 

 quired variations take place, is due either to the retention of the 

 deciduous canines and molars, or to the retardation in development 

 of the permanent bicuspid teeth? 



The region of these teeth is an exceedingly active one within the 

 maxilla since the germs of the permanent canine and of the bicus- 

 pids are well advanced to completion. At the same time the pe- 

 ripheral structures are not changing in correspondence. Hence an 

 element of disturbance is created. 



Clinical applications. 



It is evident that if, as has been claimed, the rugse are modified by 

 nutritive and developmental processes they will have clinical signif- 

 icance also. The application will be especially evident in the 



