The phylogeny of the lymphatic system is still largely a matter of conjecture due to the lack of knowledge of the conditions existing in the lower vertebrates. Nearly all of the earlier studies of lymphatic systems share the disadvantage of having been dependent upon non-physiological techniques. These included such methods as the retrograde injection of metallic mercury and other substances into dead animals and the direct injection of lymphatic areas without actual cannulation of lymphatic vessels per se.
William Hewson (1769) was the first to publish a study of the lymphatic system of a reptile. Panizza (1833) investigated the lymphatic system of the loggerhead turtle and described for the first time the posterior lymph hearts of reptiles. Weber (1835) studied the lymphatic system of Python tigris and reported that the major lymphatic vessels were periarterial structures surrounding the major arteries and connected to these arteries only by connective tissue trabeculae crossing the lumen of the enveloping lymphatic vessel. Chapman and Conklin ( ' 3 5 ) reported the existence of similar periarterial vessels in snakes. The posterior lymph hearts of Alligator mississippiemis were described by Spanner ( '29). The only other recent works concerned with the study of reptilian lymphatics which have come to the author's at-'This is a part of a doctoral dissertation done with the