180 OTTO FREDERIC KAMPMEIER 



Are the discontinuous thoracic duct rudiments, hke those of the 

 ventral cephahc sinus in Amphibia, derived from endothelial 

 proliferations which have severed their connections with the 

 parent veins and have acquired lumina, subsequently to meet 

 and become confluent with one another to create a continuous 

 channel? Is the relation of these isolated cavities to some of the 

 confused group of Mayer-Lewis anlagen a much more intimate 

 one than has been supposed by most investigators? 



Recently the discussion has centered largely around an in- 

 jected and sectioned pig embryo, series no. 23a, of the Johns 

 Hopkins University Embryological Collection. Professor Sabin 

 originally held^ that the developing thoracic duct in this specimen 

 was completely filled with the injecta. Some time later the writer 

 was given the privilege of examining and describing this particular 

 embryo. He pointed out^ the existence of a long, blind, dilated 

 space which follows closely upon the injected portion of the duct 

 and is sharply demarcated from the neighboring veins as well as 

 from the indefinite connective tissue interstices, a contrast 

 admirably brought out in the photographs published at that time. 

 Habin now argues'' that the injection in this case was not a per- 

 fect one. She accepts the space as a part of the thoracic duct 

 anlage, but assumes, firstly, that it is united with the injected 

 vessel by a very frail connection, which, if at all possible, must be 

 extremely difficult to distinguish from the surrounding tissue 

 reticulum, and secondl}^, that the pressure of the injection was 

 entirely inadequate to force the fluid through the narrow passage. 

 Leaving aside a consideration of the contradictory evidence which 

 has been explicitly expressed in previous papers,^" the writer 

 would ask Professor Sabin, whether her explanation of discon- 

 tinuities in an inchoate lymphatic duct is the most likely one, in 

 view of the observed conditions in Amphibia. The view of the 



^ In a report before the American Association of Anatomists, Ithaca, 1910. 



^ Kampmeier; Anat. Rec, vol. 6, no. 5, Jmie, 1912. 



' Sabin; Anat. Rec, vol. 6, no. 7, August, 1912, and Johns Hopkins Hos])ital 

 Reports, new series, no. 5. 



'" Kampmeier; Am. Jour. Anat., vol. 13, no. 4, September, 1912, and Anat 

 Roc, vol. 6, no, 5. 1912. 



