PLATE VII. 



Enchodns petrosns Cope. 



Figure 1. — Diagram of the palatine bone, lateral view, showing the 

 course of the larger blood vessels, represented in black, supplying the 

 fang and the caudal end of the bone. The lines A-O. A-1 A-2, etc., repre- 

 sent planes of horizontal sections shown in the following figures, which 

 are numbered to correspond. The sections were obtained by grinding off 

 the bone slowly, beginning on the ventral side, and, at the various levels 

 indicated, carefully drawing the surface exposed. After reaching the 

 level A-9, the bone was ground parallel to this plane until the level indi- 

 cated by line B-X was reached, after which B remains constant, the 

 planes of succeeding sections, 10 to H, all passing through it. a, b, c, d, 

 e, f, g and /; represent the ventral ends of a number of canals in the 

 osteodentine, which served successively as the main blood supply of the 

 great palatine tooth. Before the tooth was sectioned the ventral ends of 

 these canals were indicated by dark spots on the surface, one occurring 

 about the center of each crescentic scar. (See fig. 15, pi. XV.) These 

 canals are found to proceed dorso-caudad, and soon the posterior five 

 anastomose and change their course to dorso-mesio-cephalad and emerge 

 on the mesial surface of the bone at the point i. The canals beginning at 

 6 and c proceed in the same general direction as those mentioned, and, 

 after anastomosing, open to the mesial surface at two places very near 

 point B (also indicated in fig. 8, ch) ; a marks the open end of the canal 

 which led to the fang, the latter having been broken off of this palatine. 

 This canal was traced to a point at the level of A-8, where it opened to the 

 mesial surface (fig. 9, a). The outline of the basal portion of the fang 

 is shown, and the continuation of the canal down the fang is indicated 

 by a broken line. The large vessels in the caudal end of the bone are shown 

 to belong to a system distinct from the canals in the osteodentine. Its 

 main trunk proceeds dorsally through the osteodentine, giving off few 

 branches until it reaches the true bond above, when it is found to branch 

 profusely. At about the level A-9 its cross section was found to elongate 

 cephalo-caudally. At the level B-10, it has divided into four or five large 

 vessels having an elongate cross section and many small anastomosing 

 vessels. Continuing dorsad, the vessels become slightly grouped at the 

 level B-12, and at the level B-H the five larger ones are in cross section 

 as shown in the section taken at this place (fig. 14), and, retaining the 

 same size, shape and position relative to each other, they now proceed 

 dorso-cephalad until they emerge on the dorsal surface of the palatine. 

 The outer edges of four of these parallel canals are represented in the 

 diagram (fig. 1) ; the fifth one \y, fig. 14), being situated directly mesial 

 to the others, could not be shown in the diagram. Only the edges are 

 represented, as the canals are elongated in cross section and overlap so 

 that they can not be shown full size (figs. 13, 14). Most of the palatines 

 show the openings of these canals on the dorsal surface. 



Figures 2 to 14, inclusive, are numbered to correspond to the various 

 levels indicated in the diagram, indicating horizontal sections taken at 

 these levels. The external side of the bone is uppermost in the sections. 

 Cross sections of canals are represented in black. Point A, figure 1, 

 corresponds to line A- A in figures 2 to 9, inclusive; point B in figure 

 1 to line B-B in figures 10 to 14, inclusive. The lettering in all of 



