60 MR. F, E, BEDDARD ON THE ENCEPHALIC [May 16, 
§ Brain of Iguana tuberculata. 
The plan of the cerebral arteries in this Lizard differs in a 
number of particulars from that which will be shortly described. 
The anterior spinal artery, though of considerable size, is yet 
of less calibre than the basilar, with which it is nevertheless in 
perfect continuity. The exit of the posterior pair of cerebellar 
arteries marks the middle of the medulla. These arteries are 
slightly asymmetrical, the left being a little in advance of the 
right. They arise behind the point of origin of the 6th pair of 
cranial nerves. The anterior pair of cerebellar arteries arise just 
after the division of the basilar artery to form the carotids on each 
side; they are distinctly smaller than the posterior pair. 
The two branches of the basilar are approximately equal in size, 
as are the carotids which join them very shortly after the bifur- 
cation of the basilar. The point of junction is just at the point 
of origin of the anterior cerebellar arteries: In this, it will be 
observed, is a slight difference from the figure of the cerebral 
arterial system of this Lizard given by Rathke*. The next artery 
arising from the circle of Willis is in front of the third nerve 
(to the inside of which nerve passes the forward continuation of 
the carotid, as in other vertebrates) and supplies chiefly the corpus 
bigeminum of its side ; but it also gives off a branch each to the 
cerebellum and to the cerebral hemisphere. A little way anterior 
to this is a much more slender vessel which is absolutely 
symmetrical on both sides of the body and which almost at once 
divides into two branches; one of these ends upon the in- 
fundibulum, the other reaches the optic nerve of its side. Beyond 
this again arises the posterior cerebral artery. This artery reaches 
the hemisphere just at the furrow which divides it from the 
corpus bigeminum and runs parallel to the cerebral branch of the 
bigeminal artery. 
A little further forward the carotid finally divides into two 
arteries. The outer and stronger branch may be termed the 
middle cerebral; it runs forwards, curving outwards in the middle 
so as to be crescent-shaped, to the long and slender olfactory bulbs, 
giving off numerous slender branches to the hemisphere on its way. 
The inner branch very soon again divides into two: the innermost 
of them is the ophthalmic artery; the outer runs forward along 
the median ventral line of the brain in close contact with its fellow 
of the opposite side. 
* “ Untersuchungen itiber die Aortenwiirzeln &c. der Saurier,” Denkschr. k. Akad. 
Wiss. Wien, xiii. 1857, p. 51. 
[Since this paper was read Mr. R. H. Burne has kindly directed my attention to a 
paper by Dr. Hofmann in Zeitschr. f. Morph. u. Anthr. ii. 1900, in which the arterial 
system of the brain is described in a number of Fishes, Amphibia, Birds, and 
Mammals, and in the following Reptiles, viz. Iguana, Tropidonotus natrix, Croco- 
dile, and Testudo greca. That of the last alone (among Reptiles) is figured. This 
paper has been apparently overlooked by the recorders of the Mammalia, Aves, and 
Reptilia in the ‘ Zoological Record’ for 1900; but it is catalogued by the recorder of 
“General Subjects.”’—July 6th. | 
