644 Jacob Parsons Schaeffer. 



of the anterior and inferior surfaces of the body of the sphenoid 

 bone ffig. 21). These meatuses in a general way possess knees or 

 bends, thus presenting ascending and descending rami. These 

 bends are best marked in the middle and superior meatuses. It is 

 a constant condition in the middle meatus, and a fairly large num- 

 ber of specimens show a well marked ascending ramus for the 

 superior meatus. The remaining meatuses when present, however, 

 do not have well marked ascending rami. In fact very many 

 specimens give no evidence whatever of individual ascending 

 rami for the meatus suprema I, II, and III (fig. 23). In a general 

 way it may be stated that the differentiation of ascending rami 

 becomes gradually less marked as we pass from the meatus medius 

 to the meatus suprema III (figs. 21, 23, and 25). 



The ascending rami. The ascending ramus of the middle meatus 

 is directed rather obliquely, in a ventral and superior direction — 

 this is less so for the corresponding ramus of the superior meatus. 

 As w^e pass from the superior meatus to the supreme meatus III 

 we find a rapid change in direction of the ascending rami to a 

 more or less vertical plane, i,e., the ascending rami more nearly 

 vertical to the cribriform plate of the ethmoid bone. We may, 

 therefore, say — when ascending rami are differentiated — that as 

 we proceed from the meatus medius to the meatus suprema III, 

 there is a gradual change in direction of the ascending rami from 

 an oblique to a more or less vertical plane (fig. 21). 



In fig. 21 we have the representation of a specimen which pre- 

 sents an ascending ramus for each corresponding meatus. The 

 ascending rami of the supreme meatuses, II and III are, however, 

 not marked, in that the two latter meatuses seldom have well devel- 

 oped knees. In fig. 22 the ascending rami are indicated merely 

 by very shallow, short grooves near the cribriform plate of the eth- 

 moid bone. In the latter case in no instance does an ascending 

 ramus reach the corresponding descending ramus. This doubtless 

 means a lessened degree of differentiation into ethmoidal conchae 

 in the region of the ascending rami as compared with the corre- 

 sponding region in fig. 21. 



