4 ON THE ORIGIN AND DEVELOPMENT OF THE 



upper, and of the posterior parts of the lobe in the lower jaw, 

 the cut surfaces of the cheeks made by the scissors were seen 

 (I l t 1 1). 



The mucous membrane over its whole extent was thin, and 

 of a greyish-yellow colour, the lobes granular, very friable, and 

 of a dead white. The breadth of the upper alveolar arch was 

 14 line, and the length of the same was 1 line. 



2. The jaws of an embryo which measured 1 inch, weighed 

 20 grains, and appeared to be about the seventh week, were 

 prepared and examined as in the former case. 



Upper Jaw. The free edge of the lip (a, Fig. 4) was not 

 so extended as at the sixth week. 

 The horse-shoe lobe (c) had become 

 broader and more developed pos- 

 teriorly, and anteriorly exhibited 

 three lobules, one median (m), and 

 two lateral. and anterior (n n). The 

 two lobes observed on each side of 

 the palate in the former embryo (d 

 d, f /, Fig. 2), had disappeared, hav- 

 ing apparently coalesced ; the posterior one (/) being curved 

 forwards to join the anterior (d), in the point (s t Fig. 4), while 

 the combined mass had contracted itself towards the front 

 of the mouth within the limits of the horse-shoe lobe (c). 



The cleft had slightly diminished, but was still of sufficient 

 width to display the whole of the undivided nasal cavity. 



The lip (a) was so lax as to admit of being moved by the 

 middle. The horse-shoe lobe (c) could also be pressed by the 

 same means inwards and backwards. When these two parts 

 were separated, the mucous membrane was seen to form a 

 duplicature (&), between the lips and a ridge (0), which ex- 

 tended from the posterior part of the dental arch to the outer 

 extremity of the lateral lobule (n). 



