124 CAVITIES OF THE NOSE. 



which have been described at page 76. It extends from the sphe- 

 noid bone, very near to theossanasi ; and is uniformly flat and rough. 



About the middle of it begins a deep groove, which penetrates 

 into the cellular structure of the ethmoides, and passes obliquely 

 downwards and backwards. At the upper end of this groove is 

 the foramen by which the posterior ethmoidal cells communicate 

 with the nasal cavity. 



This is the upper channel &r meatus of the nose. At the 

 posterior end of it is a large foramen formed by the nasal plate 

 of the os palati and the pterygoid process of the os sphenoides, 

 and therefore called pterygo or spheno-palatine foramen. It 

 opens externally, and transmits a nerve and an artery to the nose. 



Below the meatus is the upper spongy bone, which presents a 

 convex surface ; its lower edge is rolled up and not connected 

 with the parts about it. This spongy bone covers a foramen in 

 the ethmoid bone, by wbich its anterior cells and the frontal 

 sinuses communicate with the nose. 



Below this spongy bone is the middle channel, or meatus of 

 'the nose. The channel extends from the anterior to the poste- 

 rior part of the cavity. It is very deep, as it penetrates to the 

 maxillary bone. The cells of the ethmoid are above it; the 

 inferior turbinated bone below it ; and the upper spongy bone 

 projects over it. In this channel is the opening of the great 

 cavity of the upper maxillary bone. At the anterior extremity 

 of it is a small portion of the os unguis, which intervenes between 

 the nasal process of the upper maxillary bone and the cells of 

 ihe ethmoid, and continues down to the lower spongy bone. 



The lower spongy bone is nearly horizontal, and very conspi- 



sinuses and anterior ethmoid cells ; the triangular aperture immediately above 

 the letter is the opening of the maxillary sinus, i. The inferior turbinated bone. 

 Jc, k. The inferior meatus. I, L A probe passing up the nasal duct, showing the 

 direction of that canal. The anterior letters g, /;, are placed on the superio? 

 maxillary bone, the posterior on the palate bone. m. The internal pterygoid 

 plate, n. The hamular process. 0. The external pterygoid plate, p. The situa- 

 tion of the opening of the Eustachian tube. q. The posterior palatine foramina, 

 the letter is placed on the hard palate, r. The roof of the left orbit. 5. The 

 optic foramen, t. The groove for the last turn of the internal carotid artery 

 converted into a foramen by the development of an osseus communication be- 

 tween the anterior and middle clinoid processes, v. The sella turcica. z. The 

 posterior clinoid process. 



