56 Florence E. Sabin. 



which they termed subintimal, proved to be only tissue spaces and 

 they withdrew this work in 1907. 



At this time they presented the development of the jugular lymph 

 sacs in the cat, agreeing entirely with the work of Lewis and myself ; 

 but in connection with the rest of the system they at that time agreed 

 entirely with Sala, believing that the peripheral vessels were dilated 

 tissue spaces. In the Anatomischer Anzeiger of 1908, McClure gives 

 up entirely the theory of the origin of the lymphatics from tissue 

 spaces and comes to agree with Lewis that sections show multiple 

 anlagen. As I have already said, the multiple anlagen of Lewis 

 are undoubtedly in sections and to interpret them is the crucial 

 point. They cannot be interpreted through sections alone ; and 

 merely repeating the observation of them in sections does not add to 

 our knowledge of their interpretation. They must be subjected to 

 some kind of an experiment. The inadequacy of simple observa- 

 tion to intei*pret them was clear to Lewis for he refrained from mak- 

 ing an interpretation. The experience of Huntington and McClure 

 serves to emphasize strongly the inadequacy of sections alone, and 

 the large part of that personal equation plays in interpretation, for 

 from practically the same type of material they have taken succes- 

 sively three different standpoints. 



In tliis laboratory under the direction of Professor Mall a group 

 of people have been subjecting these numerous anlagen of Lewis to 

 some sort of experiment. Dr. Eliot R. Clark^^ has been studying the 

 blood vessels and lymphatics in the living tadpole's tail. His speci- 

 mens prove Langer's suggestion that lymphatics grow by the sprouting 

 of their endothelial lining cells by making it possible to watch them 

 grow. His observations and descriptions of these lymphatic capilla- 

 ries, sending out long sprouts that now move forward, now bend out 

 of their course to pick up some stray blood corpuscle and now retreat, 

 make one realize how little sections show us. Certain of his observa- 

 tions are exceedingly fundamental, first in the non-lymphatic zone 

 in the living specimen there are no isolated anlagen. This you can 

 never say with certainty in sections because as will be shortly proven 

 lymphatics can be demonstrated b}^ injection where they cannot be 



^^Clark, Anat. Record, Vol. Ill, 1909. 



