372 Grant Sherman Hopkins 



cardial sinus (Fig. lo). The action of the valve at this open- 

 ing, as determined by insufflation, permits only the ingress of 

 fluids and it is by this opening, doubtless, that the lymph of 

 the pericardial sinus enters the lymph sinus of the lateral 

 lymphatic vessel, and from thence enters the veins. 



At the caudal end of the body the lateral lymphatics 

 terminate in the caudal vein. The correlation of the lymph 

 and blood vessels at this point is somewhat complex. The 

 lateral lymphatic extends caudad, nearly or quite as far as the 

 dorsal fin, when it suddenly bends at right angles and extends 

 between the muscles directly towards the meson. Close to 

 the sides of the vertebrae the vessel opens into a 13'mph sinus 

 extending along the side of the axon (Fig. 11, s). Conse- 

 quent on the dorsal inclination of the terminal portion of the 

 axon, the lymph sinus lies at an angle to the general direction of 

 the lateral lymph vessel. In a specimen measuring 53 c. m., 

 the sinus was about i c. m., long and from 3 to 5 millimeters at 

 its greatest width. At its cephalic end the sinus opens into the 

 caudal vein. The orifice between the two vessels is closed b}^ 

 a valve which readily permits the flow of lymph into the 

 veins but prevents any flow in the opposite direction as was 

 repeatedly demonstrated by alternate insufflation and 

 aspiration of the caudal vein. The sinus communicates with 

 its fellow of the opposite side by at least two small connecting 

 branches, passing directly from the mesal side of one sinus 

 into the corresponding side of the other. Joining the lateral 

 lymph vessel shortly after it turns toward the meson, is a 

 large branch which extends dorso-caudad to near the dorsal 

 edge of the caudal fin and then turns cephalad and is con- 

 tinued along the body as the dorsal lymphatic (Fig. 11, r.). 



The correlation of the lateral lymph and blood vessels was 

 found to be the same on either side of the body. 



The lymphatic vessel on the ventral side of the body begins 

 as a large vessel along the base of the caudal fin, and extends 

 directly cephalad till it reaches the level of the heart where it 

 divides into two branches which lie between the pericardium 

 and the tough fibrous partition separating the pericardial 

 from the abdominal cavity. On its course, it receives the 



