Kneeland on the Anatomy of Crocodilus lucius. 111 
arises, does the venous blood of the left aorta pass into the 
pure blood of the right, or the contrary?  Panizza believes 
the latter, according to Bischoff, from the simple fact that a 
sound passed more easily from the right to the left aorta than 
the opposite. Cuvier (op. cit. p. 317,) says this opening is to 
*introduce a small quantity of oxygenated blood into the 
left (or venous) aorta." 
Dr. Harlan! (in his notes of a dissection in 1824,) forced 
air into the vena cava ascendens, which injected the right 
auricle and ventricle, and passed into the pulmonary artery, 
venous aorta, and into the true aorta through the valvular 
opening at its base. He forced air also into the pulmonary 
veins, which inflated the left auricle and ventricle, and passed 
into the true aorta ; but it did not pass into the right side of 
the heart ; so that his experiments show that the blood passes 
from the venous to the true aorta. This is also the opinion of 
Bischoff, (op. cit. p. 7.) i 
During the contraction of the ventricles the valves of both 
aortas being firmly pressed against the opening, no mingling 
of the bloods can take place; this opening can only be of 
use during the diastole of the ventricles, when the valves open 
to prevent regurgitation, and thus leave the opening free. In 
the ordinary state of the circulation, there would probably be 
but a trifling mixture, if any ; it would be impossible to say 
in which direction this would take place, as the relative pres- 
sure in the two aortas cannot be ascertained. The time when 
this opening performs its especial function is when the animal 
is under water ; as there is then no respiration nor pulmonary 
circulation, there is of course no blood in the left ventricle, 
and none sent through the true aorta. Were it not for this 
opening, the. head and upper extremities, which are supplied 
by the right aorta, would be completely unprovided with 
blood ; we may naturally conclude that venous blood is sent 
through the opening from the left aorta to supply these parts. 
- Thus by its four cavities, the heart of the crocodile resem- 
1 Medical and Physical Researches. Philadelphia, 1835: p. 198. 
