ELEMENTS OF MAMMALIAN ANATOMY. 



The ethmoid (Fig. 18) is a single bone lying ventral 

 to the frontals and nasals. It separates the cranial 

 cavity from the nasal cavity and projects into the latter 

 in the form of two thin scroll-like plates of bone and a 

 median vertical plate. In order to see the relations of 

 this bone, three skulls must be used, one of which should 



FIG. 15. DIAGRAM OF THE BONES OF THE MAMMAUAN SKULU VIEWED 



LATERALLY. 



1, 2, 3, etc., indicate the places of exit of the twelve cranial nerves, pmx, 

 Premaxillary ; ty, tympanic, 7 and 8 are on periotic; thy, tympano- 

 hyal; shy, stylohyal; ehy, epihyal; chy, ceratohyal; bhy, basihyal; 

 thhy, thyrohyal. The cartilage bones are shaded. (From Flower, 

 after Huxley.) 



be bisected sagittally, a second should have the roof 

 of the cranial and nasal cavities removed, and the third 

 should be cut transversely on a line joining the middle 

 of the orbits. The ethmoid is usually visible externally 

 as a small rhomboid plate on the mesal wall of the orbit 

 between the frontal, lachrymal, and palatine bones. It 

 consists of four parts: the paired ethmoturbinals or 



