/.'. Sabin. 



ually invade the boch in orderly sequence in definite 



and characterise z « and layers. The growth is always in the 



illary bed, that is, all lymphatics develop as capillaries, and the 

 - to develop become the first lymph trunks or ducts. Third, 

 ethod of growth throughout is bj the sprouting of the proto- 

 plasm and the nuclear division of the endothelial of the capillary wall, 

 ultimate capillaries are distinguished bj the absence of valves, 

 hi n word, • a continuous growth and invasion of the 1 >< >< 1 \ 1 . \ 



lymphatic capillaries from the primary sprouts which bud off from 

 tin veins to the ultimate peripheral lymphatic capillarii -. 



IV. PRIMARY [A'MPHATK SYSTEM IX^ DIFFERENT 



FORMS. 



I. I'im M vi:y \.\ \iril \ I [< SACS IX THE PlG. 

 A. GEN EG \l. SI M MAR'S 01 nil - \< 5. 



I - . begin ' e section on the special anatomy of the lymph sacs 

 by .-I detailed description of the origin of the lymphatics in the | 

 since thai is the best known form. I can now describe the origin of 

 all ol the lymphatic sacs in the pig and give the relation of the main 

 ducts i" all of imitive sacs. On the basis of our knowledge of 



lymphatic system in this form I shall give whal is known of the 

 lymphatic - in other mammals, in birds, reptiles and amphibia, 



and shall then be in a position i inpare the primary lymph sacs in 



mammals with tin- amphibian lymph hearts and sacs. 



In the pig the lymphatics bud off from the veins in two places, from 

 the anterior cardinal veins and from the veins of the Wolffian body. 

 There are two sets of paired sacs, the jugular and the iliac; and two 

 unpaired sacs, the retroperitoneal and the cisterna chyli. In the most 



neral terms the jugular sacs drain the anterior half of the body; 

 the iliac sacs drain the posterior half of the body, while the retroperi- 

 toneal or prae-aortic sac drains the viscera. The cisterna chyli with 



the thoracii innects the jugular and renal lymphatics. Ini 



•ific terms the jugular lymphatics bud off from the anterior cardi- 

 nal veins, form large sacs in the neck, from which lymphatics grow 

 to the head and nek. the foreleg and thorax, and to the heart and 

 lungs. From the left sac arises the jugular stem of the thoracic duct. 

 All the rest of the lymphatic sacs hud off from the vena cava, where il 

 is ;, part of the median mesonephritic vein, from the median 



