////; i HIM 8 



tuberositios placed on each side of tho perpendicular lamina, and offering 

 for study a inidiUi' jiorlion, a base, and a nunnnit. Kach of these is formed by 

 an assemblage of numerous, extremely thin, osseous plates, curved into 

 small and very fragile; convolutions. These, elongated from above to IH!"\V. 

 become longer as they are more anterior; they are attached by their supn inr 

 extremities to tho transverse plate which separates tho cranium from tho 

 nasal cavities, and by one of their borders to a thin leaf of bone which 



envelops the lateral masses out- 

 wardly. They have received the 

 name of tho ethmoidal volutes (or 

 cells). 



Middle portion. This should 

 bo studied externally and inter- 

 nally. 



Tho external surface of each 

 ethmoidal mass is divided into two 

 sections: an internal, making 

 part of the nasal cavities ; the 

 other, external, concurs in form- 

 ing the walls of the frontal and 

 maxillary sinuses. The first, tho 

 least extensive, is almost plane ; 

 ^ parallel to the perpendicular la- 

 mina, it is isolated from it by the 

 narrow space which forms the 

 bottom of tho nasal cavities ; it 

 presents several openings which 

 separate the most superficial cells, 

 and join the internal canals to be 

 hereafter noticed. The second, 



A, Occipital bone. 1, Condyle ; 2, Con- 

 dyloid foramen ; 3, Styloid process ; 

 4, Summit of basilar process. K, Parie- 

 tal bone. 8, Parietal protnberanc-- ; 

 9, Channel which concurs to form the 

 parieto-temporal canal. c, Frontal 

 bone. 10, Transverse crests separating 

 the cranial from the facial portion of 

 the bone; 11, Frontal ..jnusi-s ; 1'J, 

 Notch on the lateral border occupied 

 by the wing of the sphenoid bone; l.'J, 

 Notch for the formation of the orbital 

 foramen; 14, Summit of the orbital 

 process ; 15, Supraorbital foramen. 

 D, Perpendicular lamina of the ethmoid 

 bone. K, K, Lateral masses of the eth- 

 moid bone. 16, The great ethmoid cell. 

 K, Squamous portion of the temporal 

 bone. 17, Saperoaadyloid process ; 

 18, Channel for the formation of the 

 parieto-temporal canal. o, Tuberous 

 portion of the temporal bone. 5, Mas- 

 toid process; 6, Internal auditory 

 hiatus; 7, Opening for the enstaehian 

 tube into the tympanum. ir, Ln'h- 

 rvmal bone. I, Nasal bone. J, Su- 

 turbinated bone. 



ANTEBIOB 

 (HORSE) 



\ ll.\\ I. II 



BONKS OP THE HEAD OF A FCKTU8 

 AT DIUTH ; DISARTICULATED, AND 

 FROM BEHIND. 



