METHODS USED IN OBTAINING AND PREPARING SPECIMENS 17 



enhaus were placed in 10 per cent formalin immediately 

 after removal from the bodies and allowed to harden in this 

 solution for a period of from eight to ten weeks, at the end of 

 which time they were sectioned in the desired plane by means 

 of very small, narrow saws. Jewelers 7 saws were used for 

 sectioning through the teeth, and small scroll saws were 

 used for other parts. The mucosa remained perfectly 

 attached in nearly all instances, and in no case were the 

 relations of the delicate bones of the ethmoid areas disturbed. 



3. In 5 cases frozen sections were made at various levels 

 in the horizontal plane. 



4. In the 18 skulls from which the soft parts had been 

 removed by maceration all accessory sinus areas were com- 

 pletely filled with paraffin before sectioning with a thin saw, 

 thus avoiding fractures of the delicate plates of bone in the 

 ethmoid area. The paraffin was removed by placing the 

 specimens in hot water. This method is of great value in 

 obtaining nearly perfect bony specimens. 



The ostia of the accessory sinuses, however, can be ac- 

 curately studied as to size, location, and exact communi- 

 cations only when the mucosa is intact. Thus these 18 

 osseous specimens were used only in the study of size, ex- 

 tent, and relations of the sinus cavities and their walls, and 

 were not included in any of the estimations regarding the 

 ostia. 



From the previously given lists it is seen that the stages 

 of development shown by these preparations form a con- 

 tinuous series from the sixtieth day of intra-uterine life up 

 to maturity, and then a few specimens from the aged. 



The development of the nasal areas earlier than the 

 sixtieth day of embryonal life will be considered only in the 



