II 



lamina of tho ethmoid bone. Tho very thin lateral portions form part of the 

 circumference of the wings ; they an; notched near their union with tho 

 middle pi- ce to assist in tho formation 

 of the orbital foramen. Tho ttn> I, it, ml 

 lionli-r* are thin and convex in their an- 

 terior half, as is also the contour of tho 

 wings, which are mortised in the frontal 

 bone. For the remainder of their extent 

 they are thick, < lei iticulated, and bevelled 

 at the expense of tho external plate, to 

 articulate with the squamous portion of 

 the temporal bone. 



St/'tK-tiin: This bone is compact on 

 its sides, and spongy in its middle part; 

 interiorly, it is excavated by the sphe- p 

 n.-idal sinuses. 



Development. It is developed from 

 two principal nuclei of ossification ; a 

 superior forms the subsphenoidal pro- 

 cess and the canal of the same name, 

 the vidian fissure, pituitary fossa, fissures 

 of the internal face, and the most pos- 

 terior of the great supersphenoidal 

 canals ; the other, the inferior, forms that 

 portion of the body hollowed by the 

 sinuses, the lateral alto, 1 and the optic 

 fossa and canals. In meeting each 

 other, these centres form the vidian canal 

 and tho two anterior supersphenoidal 

 canals. They are not consolidated with 

 each other until a very late period ; for 

 which reason they are sometimes de- 

 scribed as two distinct bones. M. POSTERIOR BONES OF THE HEAD OF A 

 Tabourin has even proposed to attach FCETI-S (HOK-I ) AT UIUTH; DISARTICU- 

 the description of tho inferior sphenoid I.ATKI. AND vn;wi i- IN i UONT. 

 to that of tho ethmoid, because it is A, Sphenoid bone, 1. Maxillary notch; _'. 

 united with this bono a long time before : ' ' ; 



it is joined to the superior portion. 



of the maxillary nerv.' ; 4, Cavernous 

 sinus; .">, Optic, fossa ; (!, (Ireat wing; 

 6', Unossitied portion of the gn-at . 

 7, Notch for the formation of the orUtal 

 foramen. B, Vomer. c, Palate bone. 

 i>, '/.\i'iw.\. K, Superior maxilla. 8, In- 

 ferior orifice of the maxillo-dental canal. 

 K, 1'reinaxillnry bone. 



6. Temporal Done. 



The temporal bones inclose the 

 cranial cavity laterally, and articulate 

 with tho occipital, parietal, frontal, 

 sphenoidal, and tho zygomatic bones; 

 also with the inferior maxilla and tho hyoid bono. Each is divided into 

 two pieces, which, arc never consolidated in tho horse ; one forms tho 

 squamous portion of the temporal bone ; tho other, tho tuberous portion. They 

 will bo described separately. 



Squamous Portion. This is flattened on both sides, oval, and slightly 

 incurvuted like a shell, a shape to which it owes its name. It offers for 

 study an / ,' rnnl and an int<-ninl face, and a circumfi-ri-iin: 



' Thr-r \\ inir.-i HIT not iinalo^oii-. In those portions of tin- splii'noiil lx>nr in Man bcur- 

 ! uaiii--. Tln-y an (h, j. : . / ,orinoii.-l\ 



