THE CRANIUM. 137 



The cells in the ethmoid bone are numerous and large, the 

 posterior ones discharge, by one or more orifices, into the upper 

 meatus. The anterior discharge into the middle meatus of the 

 nose by several orifices, concealed by the middle turbinated 

 bone. The most anterior of these cells is funnel-shaped, and 

 joining the frontal sinus, conducts the discharge of the latter 

 into the nose. 



In children of from three to eight years of age, there is at- 

 tached to the posterior part of each cellular portion of the eth- 

 moid, a triangular hollow pyramid, consisting of a single cell. 

 This pyramid arises, not only from the cellular portion, but also 

 from the posterior margin of the cribriform plate, and of the 

 nasal lamella, by which it gains a large and secure base. The 

 processus azygos of the sphenoid bone is received between the 

 two pyramids. In the base of the pyramid, communicating 

 with the nose, is a foramen, which is known in adult life as the 

 orifice of the sphenoidal sinus. The pyramid, towards puberty, 

 becomes a part of the sphenoidal bone, and then detaches it- 

 self, by a suture at its base, from the ethmoidal. As life ad- 

 vances it is greatly developed, no indication of its original 

 condition remains, and it becomes fairly the sphenoidal cell; 

 singularly differing in shape from what it was in the begin- 

 ning.* 



Being put upon the investigation of this pyramid by the late 

 Professor Wistar, with the view of ascertaining its different 

 phases of development, it has occurred to me to see it in every 

 stage, from that of a simple triangular lamina, arising from 

 the posterior margin of the cribriform plate, to the perfect hol- 

 low pyramidal slate. The preceding anatomists describe it 

 but imperfectly; it remained for that distinguished individual 

 to elucidate its real history. 



Several of the articulations of the ethmoid have been men- 

 tioned; the remainder will be introduced with the bones of the 

 face. 



* Wistar's Anatomy, vol. i. p. 31, 3d edit. 



