THE SKULL THE CEANIUM 



307 



FIG. 232. 



expansion externally of the partition, and the delicate scrolls anterior 

 to the cleft (4 W ) may be regarded as its true termination. On the 

 inside this piece forms the more complex fourth and fifth inner scrolls. 



When the surrounding pieces are all removed the outer surface 

 (Fig. 231) of the fourth piece is seen to be divided into three parts : 

 the anterior part is the external of the two masses of scrolls attached 

 to the front end of the partition ; the middle part is the partition itself, 

 forming the true floor of the ethmoidal cleft ; and the posterior part 

 bears, above, a small curved scroll (4'), the surface of which is applied 

 to the inner surface of the third piece (3) ; below this scroll is the edge 

 of the partition expanding vertically and outward, in front, for attach- 

 ment to the anterior end of the other outer pieces. At the posterior 

 lower angle is a portion of the lower scroll (4"). 



When viewed from above there are seen, beginning at the posterior 

 end, the posterior part of a scroll (4'), the sharp edge of the partition, 

 and in front, on each 

 side, the group of small 

 scrolls. The inner 

 group is numbered 4', 

 4", and the outer group 

 is numbered 4'" (Fig. 

 232). 



The inner surface 

 (Fig. 233) is made up 

 of the inner surfaces 

 of the fourth and fifth 

 inner scrolls, as already 

 described ; but in the 

 triangle left between 

 the upper and the lower 

 part of the fifth scroll 

 are two excavated areas, 

 whereof the anterior 

 triangular area accom- 

 modates the outer sur- 

 face of the sixth piece, and the posterior area accommodates the upper 

 surface of the seventh piece. 



The fifth piece appears on the outer surface of the lateral ethmoid 



Premaxi 



TRANSVERSE VERTICAL SECTION THROUGH HALF OF FACE. 



Five millimetres anterior to infraorbital foramen. Cut surfaces 

 black. (Somewhat diagrammatic.) 



