THE 
✓ 
VETERINARIAN. 
VOL. I. JUNE, 1828. N®. 6. 
ANATOMY OF THE HORSE. 
(Continued from page 152.) 
SPHENOID BONE. (OS SPHENOIDES.) 
SITUATION. Inferior and middle parts of the cranium. 
Form. It bears a striking resemblance to a bird in flight, 
with its wings and legs extended : a comparison that has given 
rise to its 
Division —into body, alse or wings, and pterygoid processes 
or legs : altogether presenting for consideration two surfaces and 
two borders. 
The Inferior Surface, irregularly convex, is distinguishable 
into three parts :—a middle and two lateral portions. The mid¬ 
dle, thick, prominent, cylindroid, and oblong from before back¬ 
wards, by its union with the basilar portion of the occipital bone 
and the body of the ethmoid, forms the base of the cranium: 
its porousness denotes muscular attachment. Between the 
middle and lateral parts, on either side, runs a narrow fissure 
denominated the pterygoid, which leads into two small canals, 
one entering the cavity of the nose, the other the orbital hiatus : 
the fissure affords a passage to the pterygoid branch of the por- 
tio dura.—The lateral divisions send forth by the sides of the 
fissures the pterygoid processes, which project downwards and 
forwards, form a union with the palate bones, and afford attach¬ 
ment to the internal pterygoid muscles. At the bases of these 
processes are the pterygoid foramina; above and internally to 
the base is the orbital hiatus, a considerable aperture, obliquely 
ovoid from above downwards, opening into the back of the 
orbit, and including the supero-posterior and infero-posterior or¬ 
bital foramina : the former transmitting the opthalmic nerve , 
and artery, and the third pair of nerves; -the latter, the superior 
VoL. I.-No. 6. . X 
