694 
PROFESSOR T. J. PARKER ON THE 
carotids, for the head arteries of fishes, altogether, and to follow Muller in the use of 
the terms “anterior” and “posterior” carotid; at least until the embryology of the 
vessels is thoroughly made out in a large number of forms. At present any attempt 
to introduce a systematic nomenclature applicable to the whole of the Vertebrata 
could, it appears to me, only result in failure. 
The pseudobranchiai artery gives off no branches until it ramifies in the pseudo¬ 
branch (Plate 35, figs. 6 and 10, Psbr. A.), from which the blood is collected by the 
anterior carotid artery (Ant. car. A.). This vessel passes inwards and forwards along 
the floor of the orbit, crossing ventrad of the posterior carotid (Post. car. A.). It 
sends off a small ophthalmic artery (Ophth. A.) to the eye, and then almost imme¬ 
diately enters the carotid foramen, an aperture in the skull wall about 5 mm. caudad 
of the optic foramen. Having entered the carotid foramen it passes obliquely inwards 
and forwards (fig. 6) through the thick perichondrial lining of the skull, is joined by 
the anastomotic branch w from the posterior carotid of the opposite side, and emerges 
into the cranial cavity as the cerebral artery. 
The main cerebral artery (Plate 35, figs. 6 and 8, Cereb. A.) is a short trunk; it 
divides almost immediately, opposite the mesencephalon, into an anterior and a pos¬ 
terior cerebral. 
The anterior cerebral artery (Ant. cereb. A.) passes forwards along the outer and 
ventral side of the prosencephalon, to which it sends a considerable branch, and finally 
breaks up into a brush-work of small arteries on the ventral surface of the olfactory 
lobe. 
The posterior cerebral artery (arteria profunda cerebri, Hyrtl, 11) gives branches 
to the diencephalon, mesencephalon, and cerebellum (Post, cereb. A.), and, passing to 
the ventral face of the medulla oblongata, unites with its fellow in the middle line, 
forming the median myeloncd artery (arteria spinalis inferior, Hyrtl, 11), which 
(Myel. A) is continued along the ventral face of the spinal cord. 
According to Hyrtl (11) the blood, in Raja and Torpedo, reaches the cerebral 
artery, not, as described above, by the anterior carotid, but by the anastomotic branch 
w, which he calls the internal carotid (vide infra, p. 695). Part of the blood from this 
trunk is then taken by the anterior carotid (zufiihrendes Gefass der Spritzlochkieme) 
to the pseudobranch, and thence by the pseudobranchiai artery (abftihrendes Gefass 
der Spritzlochkieme) to the first efferent branchial artery. So that, according to 
Hyrtl, the anterior carotid is the afferent, the pseudobranchiai artery the efferent 
trunk of the pseudobranch. 
It seems to me that the relative sizes of the vessels sufficiently disprove this theory 
as far as Mustelus is concerned, the anterior carotid being a comparatively large vessel, 
many times larger than the anastomotic branch w, which is supposed to supply both it 
and the cerebral artery. In Callorhynchus, again, in which the anastomotic branch w 
is absent, the anterior carotid (Plate 36, fig. 17, Ant. car. A) obviously becomes the 
cerebral (or more accurately cerebro-rostral) artery. So that I can see no reason tor 
