290 



MAMMALIAN ANATOMY 



Its lateral surfaces and the posterior part of the upper surface are in 

 close contact and more or less coalesced with the bones which form the 

 walls of the nasal cavity, namely, the froutals and orbitosphenoids 

 of the cranium (Fig. 200) and the maxillaries, nasals, lachrymals, and 

 palatines of the face (Fig. 210). A portion of the lower surface is 

 united with the voiner. The greater part of the anterior end is free in 

 the nasal cavity, and may be seen by looking into the anterior nasal 



FIG. 210. 



Ends of Lateral Ethmoids, enter Frontal Sinuses. 



Ethmoid (Cribriform 



Ends of Lateral Eth 

 molds, enter Sphenoid 

 al Sinuses. 



Right Lateral Ethmoid. 



\ 



* Right Maxillary (Nasal Process). 



Right Lachrymal. 



Right Palatine. 



Right Maxillary (Body). 



Right Malar. 



BONES OF THE FACE, WITH ETHMOID IN POSITION. VIEWED FROM ABOVE, 

 BEHIND, AND THE RIGHT SIDE. (Natural size.) 



aperture. Except for a small variable spot on the inner wall of the 

 orbit, the ethmoid is not visible on the exterior of the skull. When 

 the investing bones are removed, the ethmoid is seen to have some- 

 what the form of "a cube, compressed, however, laterally, so that its 

 greatest width is slightly less than its height, which in turn is one- 

 third less than the length. It is highest at the back and lowest in 

 front. Its greatest width is between the lower anterior angles or 

 directly above them at the posterior end of the anterior quarter of the 

 length. 



On closer examination the ethmoid is seen to be composed of five 

 parts : 



Of these, two large similar vertical lateral masses, made up of bony 

 cells, lie on each side of the middle line and together compose almost 

 the entire bone ; they are called the lateral ethmoids, or ethmo- 

 turbinals. 



Situated between these, and almost in contact with their inner 

 surfaces, is a thin vertical plate, known as the mesethmoid, or per- 



