132 ADAM M. MILLER 



As regards the particular case of the thoracic duct, Sala (10) 

 in 1900 published the results of his work on the chick in which 

 he holds that it develops by canalization of solid mesenchymal 

 cords. In 1902 Sabin (11), after working with the injection 

 method, published her account of the development of the lym- 

 phatic system in pig embryos. In this she reinforces and extends 

 the view of Langer (12) and Ranvier (13), that lymphatics arise 

 from veins by a process of sprouting and centrifugal growth, 

 maintaining that the system as a whole is developed by blind 

 ducts that 'bud off' from the veins of the cervical and inguinal 

 regions, widen out to form sacs from which lymphatics grow to 

 the skin, stating also that "at the same time a growth of ducts 

 occurs along the dorsal line following the aorta to make a tho- 

 racic duct from which lymphatics grow to the various organs." 

 The two views expressed by Sala and Sabin are thus diametrically 

 opposed, the one being that the lymphatics arise in the mesen- 

 chyme independently of the veins, the other that the lymphatics 

 are outgrowths from the veins. 



In 1905 Lewis (6) expressed the view that in the rabbit the 

 lymphatic system is derived directly from the embryonal veins, 

 multiple detached portions of these becoming confluent to form 

 the permanent systemic lymphatics, stating that the thoracic 

 duct "arises from a plexus of lymphatics surrounding the aorta" 

 (p. 109). 



In 1907 Huntington and McClure (25), studying the develop- 

 ment of lymphatic vessels in their relation to the veins in embryos 

 of the cat, found that "the lymphatics begin as extra-intimal 

 spaces along the course of the primitive embryonal veins. They* 

 subsequently become confluent and form continuous vascular 

 channels" (p. 42). 



Huntington, in 1908 (14), while retaining this view of the gene- 

 sis of the systemic lymphatic vessels, as distinguished from the 

 jugular lymph sacs, defined the latter as the connecting links 

 between the hemal vascular system and the general system of 

 the lymphatic vessels, which "arise, not by transfonnation of 

 veins, but by the formation of spaces lying outside the intimal 

 lining of the veins, which spaces, becoming confluent, form the 

 general lymphatic channels of the body" (p. 25). 



