William Snow Miller 447 



of the pulmonary artery in the lung lateral branches are given off, some- 

 times from opposite sides of the main trunk, more frequently, alternately 

 from one side, then, the other. These branches are so arranged that, as 

 a rule, an arterial radicle lies between two venous radicles (Fig. 1). 



Arising from the main arterial trunk, and also from its branches, is 

 a rich network of capillaries which is spread out over the entire inner 

 surface of the lung; the venous radicles take their origin from this 

 network (PI. II). ISTot infrequently small branches of the main artery 

 extend across one or the other side of the lung and enter directly into 

 the main venous trunk. This direct union of artery and vein is quite 

 common in some lungs, while in others it is entirely absent. In some 

 instances two small arterial radicles will join the end of a venous radicle 

 giving the appearance of a vein arising from the main artery by a forked 

 extremity. Examples of each type can be seen in Plate II. 



The pulmonary vein (Fig. 1, P. Y) extends along the ventro-lateral 

 side of the lung. It is formed not only by the capillaries, into which 

 the pulmonary artery breaks up, entering it directly, but also by venous 

 radicles which take their origin from the same capillary network. As 

 the lungs converge to unite on the ventral side of the oesophagus the 

 pulmonary veins leave the side of the lung and cross it obliquely to meet 

 and fuse in the mid-line into a single vessel (Fig. 1, P. V., and PI. I., 

 Fig. 2). From this point of union the now single pulmonary vein 

 runs anteriorly towards the heart; passing to the dorsal side of the two 

 arms of the hepatic sinus it usually continues along the wall of the left 

 arm of the sinus and opens into the left side of the atrium of the heart 

 (Fig. 3). 



This description of the pulmonary blood vessels differs very materially 

 from that given by Suchard for Triton and Salamandra. Suchard re- 

 verses the course and position of the artery and vein from what I have 

 found to be the case in Necturus; the artery, according to his descrip- 

 tion, occupying the position of the vein and the vein that of the artery. 



In still another important particular does the distribution of the 

 blood vessels in Necturus differ from that given by Suchard for Triton 

 and Salamandra. In Xecturus there is no interruption of the capillary 

 network over the pulmonary vein; Suchard describes such an interrup- 

 tion in Triton and Salamandra. In Necturus the capillary network is 

 spread out over both artery and vein. 



The Lymph Vessels. — Broadly stated, the lymphatics follow the 

 blood vessels, both arteries and veins ; their arrangement, however, about 

 these vessels is different. 



