670 Jacob Parsons Schaeffer. 



Because the anlages of the paranasal chambers have primi- 

 tively different relations, Killian divides them thus : 



^'1. solche, die zwischen je zwei Hauptmuscheln (I. Ordnung); 



2. solche, die zwischen einer Haupt- und einer Nebenmuschel 

 (II. Ordnung) und 



3. solche, die zwischen je zwei Nebenmuscheln gelegen sind 

 an. Ordnung)." 



Varying views have been advanced by different writers as to 

 the genesis of the paranasal chambers. Dursy thought that the 

 establishment of all the accessory air spaces of the nose, with the 

 exception of the anlages of the maxillary and sphenoidal sinuses, 

 was wholly dependent upon resorptive processes taking place in 

 the cartilaginous and bony framework of the nose. This is cer- 

 tainly not the earliest factor involved in the estabhshment of 

 anlages. Others, who worked this region in some of the lower 

 forms, considered the space included by the lateral curling of 

 some of the conchae as ethmoidal cells — a view that is not ten- 

 able. Seydel in a subsequent paper, comes nearer the truth 

 whenhe writes: '' . . . . ihre Entwicklung von den Spalten 

 zwischen je zwei (auch rudimentaren) Muscheln ausgeht." 



Killian in '96, in an exhaustive paper, places to my mind the 

 genesis of the paranasal chambers on a sound basis. My obser- 

 vations in the main agree with his. Whether, as Killian's sche- 

 mata suggest, coalescence takes place between neighboring folds 

 and conchae, thus constricting off a portion of the respective fur- 

 row to become the anlage of a cell, seems to me a difficult problem 

 to solve. I rather hold that the nasal mucous membrane in the 

 position of the furrow pouches in the direction of a future cell — 

 this closely simulating coalescence of neighboring accessory 

 folds, or an accessory fold and a concha at these points There 

 seems to be an inherent tendency for the nasal cavity early to 

 enlarge its surface area by the formation of furrows, folds, and 

 pouches. It indeed seems difficult to decide whether, for example, 

 in figs. 36 and 44, the frontal folds or conchae coalesced with 

 each other, thus forming blindly ending furrows, or whether the 

 frontal furrow^s pouched in the frontal direction, thus simulating 

 coalescence but making it only apparent rather than real. It, 



