6 



reviews of Kampmeier ('12), Huntington ('14), especially 

 Schulte (14), McClure ('15, '21), where the literature oppos- 

 ing Doctor Sabin's views is fully described and the injection 

 method and its results extensively criticized. Kampmeier 's 

 more recent papers on the toad ('15- '25) must also be in- 

 cluded in this group, and demand special attention from 

 readers of the present paper. On the other hand, Doctor 

 Sabin ('13, '16) analyzed the considerable literature in sup- 

 port of her conclusions and discredited claims to the contrary. 



The critical examinations of these problems by E. R. and 

 E. L. Clark ('11, '12, '15, '22, '32, '33, '37 and '37 a) are 

 especially noteworthy here for the thoroughness of their ex- 

 perimental tests in comparing injections with attempted re- 

 constructions of vessels in fixed material. 



Their demonstrations in favor of the superior reliability 

 of the results of injections and in contradiction to the theory 

 of origin of lymphatics from tissue spaces seem most con- 

 vincing. 



Any discussion of lymphatics must include full recognition 

 of the contributions of the Clarks to the essential character- 

 istics of vessels of this system as studied in the living. 



These researches published in a long series of papers since 

 1^09 are certainly of first importance to students of lympha- 

 tics as they furnish much valuable material for comparisons 

 with the results of other methods of studying the system. 



They are particularly applicable to work on the develop- 

 ment of the lymphatic system in the frog, since the Clarks' 

 early studies were almost exclusively on end branches in the 

 tail fins of anuran larvae and knowledge of the behavior of 

 such unit vessels is vital to understanding of the entire system. 



Doctor Clark published his first papers in 1909 and 1912 

 with elaborate records and drawings of the anatomical char- 

 acters, relations to tissues and to developing blood vessels, as 

 well as the behavior of individual lymph vessels kept under 

 observation for long periods of time while actively growing. 

 In these papers and in a series of later studies, to which Mrs. 

 Clark added much of value, this work on the characteristics 

 of living lymphatics and development of blood vessels was 



