Lateral Wall of the Cavum Nasi in Man. 653. 



tendency of the conchae to become straighter as one proceeds 

 from the concha media to the concha suprema III is well illus- 

 trated in this figure (21). 



In other cases the individuality of the ascending crura is only 

 faintly indicated by very shallow grooves throwing into slight relief 

 extremely rudimentary crura. In fig. 22 we have such an example. 

 Here we find the genei'al ascending-crural mass well developed, 

 but the differentiation into five ascending crura, with the single 

 exception of the ascending crus of the concha media, only shghtly 

 marked. In some instances the ascending crus of the concha 

 media stands out in bold rehef. This is especially due to a well 

 developed ascending ramus of the meatus superior (fig. 24). In 

 the latter figure the ascending ramus of the meatus superior closely 

 approaches the cribriform plate of the ethmoid bone. 



Occasionally the whole ascending-crural mass presents an even 

 and unbroken surface, there being no furrows or grooves to throw 

 any portion of the mass into relief. In such instances there is 

 no differentiation of the mass into individual ascending crura; 

 however we may consider this mass as representing the ascend- 

 ing crura undifferentiated (fig. 23). If not the latter, then we 

 must say that the individual ascending crura coalesced into a 

 general fold or mass at an earlier stage. The former theory is, 

 however, the most plausible according to my observations. The 

 general ascending-crural mass is often more or less overhanging 

 in character. Again we may have the ascending crura of the 

 concha media and superior well outlined, while the supreme group 

 (I, II, III) is represented by one fold (fig. 29). 



A reference to figs. 21 to 30 will show some of the different 

 combinations met with in the fetal specimens examined for the 

 substance of this paper. 



The descending crura. The descending crura of the ethmoidal 

 conchae are, almost without exception, better differentiated 

 than are the corresponding ascending crura. The former also 

 occupy a more nearly horizontal plane; this, however, lessens 

 as we approach the concha suprema III. The middle and supe- 

 rior conchae present the best marked descending crura. The 

 concha suprema I also frequently possesses a well marked descend- 



