18 ON THE ORIGIN AND DEVELOPMENT OF THE 



tubular, but resisted all efforts to push a fine probe or bristle 

 through them ; they were merely opaque remains of the sur- 

 faces of junction contrasting with the semitransparent 

 substance of the gums. Parallel sections through all the sacs 

 exhibited similar appearances. When the contents of the sacs 

 were examined, the pulps were found to have acquired the 

 configuration of the bodies of the future teeth. The bases by 

 which the molar pulps formerly adhered to the bottoms of 

 their sacs, and which may be denominated their primary bases, 

 had become almost divided into three secondary bases, which 

 corresponded with the internal and two external fangs of the 

 future teeth. This division was so far accomplished by the 

 advancement of the internal grey membrane of the sac, under 

 the form of small compressed canals between the base of the 

 pulp and the external spongy membrane. These canals, which 

 were three in number, one external and two internal, did not 

 meet in the middle under the pulp. Deposition of tooth-sub- 

 stance (Zahn-substanz) had commenced on the edges and 

 tubercles. 



The sacs were twice as large as their contained pulps, and 

 in the space (g, Fig. 20), which existed between them, there 

 was observed a very soft flocculent gelatinous substance, which 

 had no attachment to the pulp, and did not appear to adhere 

 to any part of the sacs, except the laminae and the parts ad- 

 joining them. 



Lower Jaw. The adhesion of the dental groove was not 

 so strong as in the upper jaw. The open portion (a, Fig. 18), 

 was fully defined, and exhibited on its floor the orifice of a 

 follicle, containing a papilla. In other respects the lower was 

 similar to the upper jaw. 



Breadth of superior arch 7 lines ; length 5 lines. 



11. 5th month. Foetus minutely injected with size and 

 vermilion. 



