LYMPHATICS IN FROG LARVAE 7 



continued with experiments, and the development of the lym- 

 phatic system in chick embryos (Clark, '20) was also studied 

 with important results. More recently the growth relations 

 and reactions of lymph vessels in the living tissues of rabbits 

 studied by the Clarks and their students, by the technique of 

 Dr. J. C. Sandison ('28), is forming another chapter in the 

 comparative anatomy and physiology of this system. 



Dziurzynski's ('11) injections of lymphatics invading re- 

 generating tissues in the tail of frog larvae give further evi- 

 dence, as do ours, of the similarity of behavior in the system 

 in all its parts to the details for individual unit vessels de- 

 scribed by the Clarks. 



After a thorough study of all this literature and consider- 

 able personal experience with the material and methods in- 

 volved, the verdict of unreliability of the reconstruction 

 method and its resulting theories appears to be warranted. 



The mere problem of determining positively the limits and 

 relations of different veins, lymphatics and tissue spaces in 

 a series of sections of an embryo is one of great difficulty; 

 but the added difficulties and uncertainties of an attempt to 

 build up these different systems from section to section into 

 a model is so intricate as to severely tax the abilities of the 

 best histologists. 



Though the main vessels may be readily identified, experi- 

 enced histologists will differ widely as to what details are to 

 be modelled as lymphatics ; yet it is the finer connections and 

 relations of details which are most important. The decision 

 on these vital points must then be left to the personal judg- 

 ment of the investigator; hence it is not surprising that re- 

 examination of such models through the use of other sections 

 or even with the same sections, or by the study of injections 

 of the regions, frequently show lack of reliability in the re- 

 constructions and lead to essential changes in opinion. 



O. F. Kampmeier was not deterred by such criticisms from 

 undertaking to furnish an account of the development of the 

 lymphatic system in the toad by the method of reconstruction 

 from sections. His series of papers from 1915 to 1925 are 



almost exclusively on the toad, and hardly justify the inclu- /< 



\ \J 



> 



v 



