Dissection of Sheep's Head. 265 



its meshes. The moist membrane which covers its bony- 

 plates in life is supplied with nerves chiefly from the Fifth 

 pair, and not from the Olfactory ; so that it does not perform 

 the function of an organ of smell like the Ethmoturbinal, 

 but rather serves to guard the entrance of the respiratory 

 passages from foreign substances, and perhaps to warm the 

 inspired air.'* 



The lower part of the median partition between the nasal 

 cavities is formed by the Vomer, a bone which in a trans- 

 verse vertical section presents the form of a capital Y, 

 receives the lower margin of the Mesethmoid between the 

 lips that rise from its superior surface, and itself com- 

 pletes the nasal septum below, by the development of a thin 

 vertical plate from its inferior surface. The Yomer extends 

 back so far as to be in apposition with the anterior termina- 

 tion of the Presphenoid ; and forwards so as to meet the Prae- 

 maxillse, being in the anterior half of its course in apposition 

 with the superior surface of the Maxilla, as far back as the 

 suture between the Palatine and Maxilla. The opening between 

 the Palatine and the Yomer constitutes the Posterior Nares. 



If now the Student will press with his finger the external 

 wall of this Posterior Nares on the line between the posterior 

 ends of the Palatine and the suture between the Basioccipital 

 and Basisphenoid, he will feel the broad Pterj^goid bones, and 

 distinguish their inferior termination in a narrow lamella 

 with a hamular process projecting backwards. It is round 



T , 1 o -1 ^ Cribriform plate ; \ 



Lateral mass of the Superior and middle Ethmotvrbinals 

 Ethmoid ("turbinated bones") 



Ethmoid" \ " Crista G alii" and ] | Posterior ossified 



of \ " Lamina Perpen- > < part 



Anthropotomy. j dicularis " ) (of Mesethmoid. 



^ , ( Cribriform plate ; ) 

 Lateral mass of the J Superior and middle J Ethmoturbinals 

 Ethmoid ( u turbinated bones " ) 



