1914.] NATURAL SCIENCES OF PHILADELPHIA. 423 



anteriorly directed vessel which may be called the internal carotid, 

 ic, since it enters the skull through the most ventral of the three 

 foramina in the exoccipital, and probably supplies the brain, though its 

 further course could not be followed; (2) a somewhat larger posteriorly 

 directed artery, oc, going to the muscles at the occipital region of 

 the skull; (3) a short laterally directed stem, z^ The last-named 

 branch, z^, in turn, leads in three directions: (a) to the coUateralis 

 colli artery through the connective x^ ; (b) a short anteriorly directed 

 vessel, e, that passes into the skull, possibly to the ear, through the 

 large foramen that lies between the exoccipital and quadrate bones; 

 it gives off a small twig, q, to the muscles in the region of the jaw 

 articulation (quadrate) ; (c) the main stem of the branch z continues 

 laterad and cephalad as one of the chief arteries, z-, to the anterior 

 region of the skull, giving off a fairly wide branch, jm\ to the large 

 jaw muscle, and then two branches, o^ and o-, to the lateral surface 

 of the eyeball and socket; it then anastomoses, just cephalad and 

 laterad to the eye, with the forward continuation, cm^ of the cor- 

 responding main stem, cm, of the common carotid, already men- 

 tioned. The vessel cm', after almost meeting its fellow in the 

 middle line, passes cephalad and laterad across the ventral surface 

 of the eye to the union, above mentioned, with the lateral branch, z^; 

 at the posterior-mesial border of the eye it gives off a branch that 

 divides into two twigs, one, o^, for the posterior eye muscles, and 

 one, e\ to the region of the ear and the top of the skull. 



At the point of union of the branches cm^ and z~ a sort of simple 

 plexus may be formed from which two vessels, n, pass to the pos- 

 terior nasal region, and two vessels pass forward along the side of the 

 upper jaw. Of the latter two vessels one, which may be called the 

 inferior dental of the maxilla, dm, is very small and extends along 

 the maxilla to its very tip, at the base of the teeth and ventral to 

 the palatine bone; the other, which is larger and may be called 

 the superior dental of the maxilla, dm', extends cephalad along the 

 mesial side of the maxilla, dorsal to the palatine bone; it sends 

 numerous twigs into the maxillary bone among the roots of the 

 teeth. After passing nearly to the end of the snout, the superior 

 dental, dm', suddenly forms a loop towards the median line and 

 passes as a straight branch, n', directly caudad, near and parallel to 

 the median plane. The branch n' extends along the floor of the 

 nasal cavity and, after giving off twigs to this chamber, ends in a 

 network of vessels, o^, on the anterior surface of the eyeball and 

 socket. 



