IOWA ACADEMY OF SCIENCES 
263 
Reighard and Jennings are incorrect in stating that the internal maxil- 
lary after giving off the middle meningeal artery “divides into three 
or four branches”, which “redivide and the twigs form a complicated 
plexus, the carotid plexus”. I agree with Tandler that the internal 
maxillary artery does not completely break up into the plexus, but its 
main trunk passes through the network of vessels formed from the small 
branches above mentioned. In many cases the vessels to form the 
plexus begin to appear as far back as the inferior alveolar artery. One 
small branch commonly arises from the base of the deep temporal artery. 
A small muscle, that runs from the external pterygoid fossa to the 
extreme inner border of the condyloid process of the mandible, is partly 
enclosed in the posterior part of the plexus. This muscle seems to have 
escaped previous notice. 
From the carotid plexus there arise a number of small vessels, and 
as one might suppose, they are subject to considerable individual varia- 
tion. From the inner border of the plexus spring three or four vessels 
that pass into the skull through the sphenoidal fissure and after uniting 
into a single trunk join the internal carotid artery. The latter vessel 
then joins the circle of V\/'illis. The circle of Willis is formed by the 
union of the tw^o lateral divisions of the basilar artery with the median 
cerebral arteries. At the point of juncture the internal carotid artery 
unites with them. Or we may adopt the view of Tandler that the inter- 
nal carotid unites with the intra-cranial part of the carotid plexus, and 
that the latter joins the circle of Willis. That the carotid plexus in 
the cat is in any way connected with the circle of Willis seems to have 
been overlooked by Mivart. According to Reighard and Jennings a large 
branch of the carotid plexus passes into the skull through the sphenoidal 
fissure and divides into a short posterior communicating branch with the 
internal carotid, and into the median and anterior cerebral arteries. 
Davison® does not give any description of a communication between the 
carotid plexus and the circle of Willis, but in one of his illustrations, 
such a connection is certainly figured. I find no evidence of the occur- 
rence of a posterior communicating branch in the sense in which Reig- 
hard and Jennings use that term. For according to them the internal 
carotid unites with the basilar artery, or the posterior cerebral branch of 
the same, and the intra-cranial branch from the carotid plexus joins the 
anterior and median cerebral arteries. Then between the 'median cere- 
bral and the internal carotid arteries there is supposed to occur a com- 
municating branch. There may be recognized a vessel that corresponds 
to the posterior communicating branch of the circle of Willis in man, 
but this is quite different from that which Reighard and Jennings believe 
to occur. 
From the dorsal side of the carotid plexus is given off a small branch 
that almost immediately passes into the cranial cavity through a small 
foreman between the alisphenoid and the orbitosphenoid bones and is 
distributed to the dura mater in the antetior part of the cranium. It 
5. Davison, A. Mammalian Anatomy with special reference to the Cat. 
Philadelphia, 1903. 
