No. 2.] HEART OF LUNG LESS SALAMANDERS. 331 



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 blood 

 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 arterial ves- 

 sels for further light on our problem. Here, however, peculiar 

 difficulties present themselves whose solution I shall not attempt 

 at this time. But it seems not improbable that, in salamanders 

 with lungs, a difference of blood pressure in the arterial trunks 

 at the time of the ventricular systole may lead to a distribution 

 of blood similar to that occurring in Rana. 



The spiral valve of the salamanders can have no control 

 over the direction of the blood which passes through the conus. 

 Its function seems to be rather to prevent the collapse and 

 obstruction of the conus, which might, in the absence of the 

 valve, arise either as a result of the strong contraction of the 

 conus walls, or from outside pressure. 



