738 ALLIS. [Vor. XII. 
fossa, in man, on each side of the pituitary body, are the 
cavernous sinuses. These sinuses receive, anteriorly, from the 
orbits, through the sphenoidal fissures, the ophthalmic veins ; 
and posteriorly, behind the pituitary body, they communicate 
with each other by the intercavernous sinuses. In Amia, in 
the same position, the eye-muscle canal lodges, on each side, the 
ophthalmic veins, which communicate with each other, in the 
adult, under the hypophysis, but in embryos behind it. In 
the cavity of each sinus, in man, lie the internal carotid artery 
and the sixth nerve ; in the canal, in Amia, lies the latter one 
only of these two structures, — the internal carotid, however, 
lying near the edge of the hypophysial fenestra, in such a posi- 
tion that it would of necessity enter the canal if the fenestra 
were slightly enlarged. In the outer wall of each cavernous 
sinus, in man, lie the third and fourth nerves and the ophthalmic 
and superior maxillary divisions of the fifth nerve ; in the upper, 
lateral chamber of the canal, in Amia, are found the same 
nerves. In man, after traversing the fossa, the internal carotid 
artery turns upward, between the optic and third nerves, and 
internal to the anterior clinoid process; in Amia it has the 
same relation to the same nerves and to the hind end of 
the basisphenoid. In man, the sphenoidal fissure transmits to 
the orbit the third, fourth, and sixth nerves, the ophthalmic 
division of the fifth nerve, and the ophthalmic veins ; in Amia, 
the orbital opening of the canal similarly transmits the third, 
fourth, and sixth nerves, the ophthalmic veins, and the radix 
profundi, which latter nerve is, in all probability, the homologue 
of the ophthalmic division of the fifth nerve in man. The 
superior maxillary nerve, both in man and in Amia, does not 
issue from the fossa with the other nerves, through the sphe- 
noidal fissure, but through a separate and more posterior fora- 
men. This foramen, in man, is said by Thane (No. 100) to be 
cut off from the sphenoidal fissure ; in Amia it is certainly not 
so cut off. The recti muscles arise, in man, from the sphenoid 
bone, near the lower end of the sphenoidal fissure ; in Amia 
they arise from the basisphenoid, at the lower end of the 
orbital opening of the eye-muscle canal, or from the floor of 
that canal, inside the opening. 

