52 ALLEN 



the metapterygoid, and after receiving the hyoidean artery 

 comes to the outer surface through a foramen between the sym- 

 plectic, hyomandibuhir, preopercular, and quadrate bones. 

 This combined vessel, which may be designated as the mandib- 

 ttlar artery (PI. i, fig. i ; Man. A), makes a sharp cephalic 

 bend, passing over the outer surface of the quadrate bone and 

 then curving inward around it to the inner surface of the man- 

 dible, where it terminates in 2 branches, which supply the ad- 

 ductor mandibulge muscles. The main branch runs alonfj the 

 inner dorsal surface of the bone, while the smaller branch sup- 

 plies the ventral portion of the muscles. 



Along its ventro-cephalic course the external carotid sends 

 off many branches in the facial region and receives one. The 

 first vessel to be given off is the sclerotic-iris artery (PI. II, 

 fig. 15 ; Scl.Ir.A.). This rather small vessel arises from the 

 dorsal surface of the carotid immediately after it leaves the 

 canal formed by the prootic process. Close to its source the 

 sclerotic-iris artery gives off caudad the most anterior cranial 

 cavity artery (P\. II and III, figs. 15 and 24; C.C.A.), which 

 penetrates the skull through the middle and the largest of the 

 prootic foramina, along the dorsal surface of the roots of the 

 V nerve, and follows up the anterior surface of facialis portion 

 of the ramus lateralis accessorius to supply the adipose tissue 

 in the anterior portion of the cranial cavity. The main trunk, 

 however, continues cephalad a short distance along the outer 

 surface of the prootic dorsad of the gasserian ganglion, and 

 here divides, one branch, the sclerotic artery (PI. II, fig. 15 ; 

 Scl.A.) continues cephalad, but laterad to the truncus supra- 

 orbitalis or ramus ophthalmicus and the orbito-nasal vein. 

 When the orbit is reached, instead of curving inward around 

 the eye with the nerve and vein, it continues in a straight line 

 over the dorsal surface of the eyeball in company with the 

 sclerotic branch of the truncus supra-orbitalis and the sclerotic 

 vein, to supply the adipose tissue surrounding the dorsal surface 

 of the sclerotic coat. The other branch is the iris artery (Pis. 

 II and III, figs. 13, 15 and 19; Ir.A.), which enters the skull 

 through a foramen bounded by the dorsal process of the jiara- 

 sphenoid, the alisphenoid, and the prootic. Together with the 



