i16 Kneeland on the Anatomy of Crocodilus lucius. 
artery, which divided into its two branches before it left the 
bulb ; the left aorta, which turned and descended to join the 
right descending aorta in front of the dorsal vertebre ; the 
carotid artery, which gave off the left subclavian artery about 
an inch from the bulb; the right subclavian artery; the 
right or true aorta which descended to join the left. Bis- 
choff (Müller's Archiv. 1836, p. 5,) says there are two caro- 
tids ; Strauss-Durckheim! quotes Meckel as making but one 
carotid, which after giving off the left subclavian, runs along 
the front of the cervical vertebrae to the head, where it divides 
into the right and left carotids. In our specimen what we call 
the right subclavian artery was cut off quite near the bulb, so 
that we could not determine whether it bifurcated like the 
carotid ; at any rate, it was very small, about half the size of 
the carotid where the subclavian was given off. It does not 
appear that Bischoff had any better authority than Meckel. 
In the partition common to the two aortas, just behind their 
valves, is the opening of communication described by Panizza ; 
it was at least 3 lines in diameter, while in the specimen of 
Bischoff it was detected only after a very close examination. 
It was completely hidden behind the valves; it was somewhat 
easiet to pass a sound from the right into the left aorta than 
the opposite. The edge of the opening was well defined, 
and of a firm consistence. 
The course of the circulation is then tlirough the vens 
eave to the right auricle, thence to the right ventricle; from 
this more than half of the venous blood ‘passes through the 
pulmonary artery to the lungs ; the remainder is sent into the 
left or venous aorta for distribution to the lowet extremities. 
From the lungs the arterial blood enters the left auricle, then 
passes to the left ventricle, thence pure, through right or arte- 
rial aorta to the head and upper extremities, and body gene- 
rally after mixture with the venous blood. un" 
It is evident that the venous and arterial blood are mixed 
through the opening in the aortic wall: the question thet 
! Traité d'Anatomie Comparative. Paris: 1843. Tome 2. 
