1914.] NATURAL SCIENCES OF PHILADELPHIA. 413 



THE VASCULAR SYSTEM OF THE FLORIDA ALLIGATOR, 

 BY ALBERT M. REESE. 



The account given by Bronn in his Thierreich is apparently the 

 onh' published description of the circulatory organs in the Croco- 

 dilia. This account, even when translated, is not very satisfactory, 

 especially because it contains no diagrams of the circulation. It 

 was, therefore, deemed worth while to work out the circulation in 

 the Florida alligator in order that we might have not only a written 

 description, but also a series of more or less accurate diagrams of 

 the veins and arteries. 



A number of departures from the description of Bronn were 

 found, some of which are noted below. 



Most of the work was done upon animals of about 30 inches 

 length, which were obtained alive from the Arkansas Alligator Farm 

 at Hot Springs, Ark. 



The arteries were injected with a colored starch mass by inserting 

 a two-way cannula into the dorsal aorta. With the blood thus 

 forced into them from the arteries, the veins could, in most cases, 

 be traced without difficulty. 



In the diagrams the outlines of the more important organs are 



accurately shown by dotted lines, and the relative diameters of the- 



blood-vessels are shown as accurately as possible by the solid Ijlack 



lines. 



The Heart. 



In the Crocodilia, as is well known, the heart is four-chambered 

 and has about the same general shape as in the higher vertebrates. 



The venous blood is emptied into a thin-walled sinus venosus on 

 the dorsal side of the heart by three large vessels and one small one. 

 The largest of these, the postcava, empties into the posterior side 

 of the sinus venosus and brings blood from the posterior regions of 

 the body; it is quite wide, but is exposed for a very short distance 

 between the liver and the heart. Two large hepatic veins empty 

 into the postcava so near the sinus venosus that they practically 

 have openings into the sinus, as is shown in a somewhat exaggerated 

 way in Plate XIII, fig. 1. Near the postcaval and hepatic openings 



