Development of the Jugular Lymph Saes. 183 
Sabin’s?7 recent statement on this subject is a retraction of her 
former view and a complete acceptance of the work of Lewis,* 
concerning which she writes as follows: 
He (Lewis) showed that there is first a plexus of veins in the region of 
the sac; these veins are in free connection with the jugular vein. Then 
the plexus of veins is cut off from the jugular and appears full of blood, 
but without venous connections. Later the plexus forms a sac and rejoins 
the main vein. After it has joined the vein it becomes empty of blood. 
This discovery of Dr. Lewis I can entirely confirm. 
In view of her present position, that the anlages of the lymph 
sacs are first cut off from and then later rejoin the veins, it appears 
to the writers that Sabin’s original observations upon the develop- 
ment of the jugular lymph sacs must have been made upon 
embryos in which the lymph sacs had already been established, and 
in which the secondary permanent connections with the veins 
had taken place, since in all of the embryos injected she found the 
lymph sacs to be in open communication with the veins. If a 
connection between lymph sac and vein served as the only eri- 
terion for inferring that the lymph sac is derived from the veins, it 
appears to the writers, in view of her more recent statement on the 
subject, that a similar and equally valid inference might have been 
drawn by observing the conditions which prevail in the adult. 
Considering our present knowledge of their development, it is evi- 
dent, from the very nature of the case, that the injection method, 
as used by Dr. Sabin, has not as yet given us the slightest clue as to 
the actual manner in which the anlages of the lymph sacs are 
derived from the veins, nor, in fact, any evidence at all that they 
even possess & Venous origin. 
The chief service thus far rendered by the injection method is 
the determination of the extent to which the lymphatic develop- 
ment has progressed in the body after the lymphatics themselves 
have been established. 
7 Loc. cit. p. 49. The Lymphatic System in Human Embryos. With a Con- 
sideration of the Morphology of the System, in The American Journal of Anatomy, 
vol. 9, 1909. ; 
8 Lewis. F. T. The Development of the Lymphatic System in Rabbits. The 
American Journal of Anatomy, vol. 5, 1905. 
