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sistance to the flow of blood must indeed be very minutely adjusted to 
separate the venous from a mixed and a mixed from an arterial blood 
issuing from the same opening with say, one-fifteenth of a second to accom- 
plish each phase. 2. Further the tracings made by Gompertz show that the 
blood reaches the pulmo-cutareous and aortic trunks at the same time and 
under the same pressure. Stili further the inspiration in the frog in- 
creases, not decreases, the intrathoracic pressure and would retard the 
pulmo-cutaneous system, and it has not been demonstrated satisfactorily 
to my knowledge that the capillary system of the pulmo-cutaneous vessels 
is actually less developed than in the systemic area. 38. The comparison 
of the various types of amphibian circulation is of interest. Bruner (1), for 
example, makes the following statement: “The fact that the septum 
atriorum disappears wifh the lungs indicates clearly that in the sala- 
manders with lungs the septum performs a certain function which becomes 
superfluous or impossible after the loss of these organs. This function is 
the separation of the venous blood of the right auricle from the aerated 
blood of the left auricle. But what is the significance of this separation 
if the two sorts of blood are afterward mixed during the passage through 
the ventricle and conus? Or is there, after all, in salamanders with lungs 
a partial separation of the aerated and the venous blood in its entire course 
through the heart? Such a separation occurs, as is well known, in the 
heart of Rana. Now as regards the atrium and ventricle, we find essen- 
tially the same structure in Salamandra as in Rana. It is true that the 
septum atriorum in the salamander is perforated, while in the frog it is 
not. But during the brief stay of the blood in the auricles the small per- 
forations which have been described would permit little mixing of the 
blood. There would be much better opportunity for this to occur in the 
ventricle, but here we have the same spongy condition in Salamandra and 
Rana. So far then, Rana does not seem to have a decided advantage over 
the salamander in respect to the separation of venous and arterial blood 
in the heart. We may therefore conclude that in the salamander, as in 
Rana, the first blood passing from the ventricle into the conus during the 
ventricular systole is chiefly venous. In Rana this is directed into the 
pulmonary artery. In the salamander, however, the structure of the 
conus does not indicate that it could influence the direction of the blood 
current. We must turn, then, to the bulbus arteriosus and the great ar- 
terial vessels for further light on our problem.” ‘The spiral valve of the 
ralamanders can have no control over the direction of blood which passes 
