Florence E. Sabiu 387 



lymph gland. Each gland then drains an area represented by the ducts 

 that grew out from the plexus. 



In the groin there are only two points of radiation for the superficial 

 lymphatics. The first or primary one is over the crest of the ileum, 

 and sends ducts over the hack and sides of the body as far up as the 

 axilla, and down over the hip. The ducts from this plexus do not 

 grow to the middle line of the body in front, but anastomose freely 

 with those of the other side across the back. The second centre, which 

 comes a little later, is in the inguinal region and sends its ducts to the 

 leg and to the ventral abdominal wall. In a pig 4.5 cm. long these 

 ducts have grown to about the level of the umbilicus and extend part 

 Avay down the leg. All the superficial lymphatics, after they have once 

 covered the skin, anastomose freely; for example, one can inject in a 

 pig 5.5 cm. long from the surface of the hip up to the axilla. 



The deep lymphatics follow the arteries, which gives the key for the 

 study of their development. By injecting along the aorta the ducts 

 to the following organs have been injected: the heart, lung, oesophagus, 

 stomach, duodenum, mesentery, adrenal, kidney. Wolffian body, repro- 

 ductive organs, pancreas, spleen and liver. The ducts to the pancreas 

 and spleen have only been injected in a pig 7.5 cm. long. I have, as 

 yet, no early injection of the ducts of the liver. Fig. 11 shows the 

 deep lymphatics of the arm and leg following the arteries. In a pig 

 7.5 cm. long the ducts following the umbilical arteries into the cord 

 have been injected, that is, the lymphatics do not pass over to the 

 umbilical cord from the abdominal wall but enter rather with the 

 arteries. The right lymphatic duct has been injected in a pig about 

 10 cm. long and its branches pass to the heart and anastomose with 

 those from the thoracic duct to that organ. 



It has now been shown that the lymphatic system in the embryo pig 

 begins as two blind ducts which bud off from the veins in the neck. 

 At the very start the openings of these ducts into the veins are guarded 

 by valves formed by the direction which the endothelial bud takes as 

 it grows from the vein. In the ducts themselves there are no valves 

 at first. From these two buds and later from two similar buds in the 

 inguinal region duets grow toward the skin and Aviden out to form 

 four sacs or lymph hearts and from these sacs the lymphatics grow 

 to the skin and cover its surface. At the same time there is a growth 

 of ducts along the dorsal line following the aorta to make a thoracic 

 duct from which the lymphatics grow to the various organs. Thus the 

 ducts of the lymphatic system gradually invade the body, but there are 



