82 OTTO F. KAMPMEIER 
ion loses weight—a source of gratification to the writer in so far 
as he is not compelled to regard his earliest work (12) as funda- 
mentally wrong in its deductions. The recent investigations 
have brushed away many difficulties, and the interpretation of 
the observations rests on firmer ground; views which were thought 
conflicting only a few years ago can now be reconciled. The 
origin of the earliest vascular anlagen in the embryo is the basic 
problem of vasculogenesis, not that of vessels, regardless of their 
vascular function, which develop later. If it be true that the 
earliest anlagen arise from the mesenchyme, as most of the 
modern research on vasculogenesis would indicate, then the two 
views of lymphatic development, the venous origin and the 
mesenchymal origin of lymph vessels, are not in diametrical 
opposition as was formerly vehemently asserted. Indeed, there 
may be a number of variations in the genesis of such channels, 
but the differences can now be judged superficial, presupposing, 
of course, that the haemal and lymphatic systems are not pri- 
mordially and phyletically distinct, as some investigators tacitly 
hold. Lymphatic anlagen may proliferate from components of 
the early indifferent embryonic vascular plexus, or certain channels 
may separate from it (just as arteries and veins are differentiated 
from it) and assume a lymphatic function; and, again, they may 
be formed directly from mesenchyme independently of vascular 
channels already existing. What determines the several varia- 
tions of lymphatic development is still obscure, although the time 
and the site at which they first appear, as conditioned by physio- 
logical needs, may be the causative factors. The first method 
is illustrated by the origin of the primary maxillary sinus which, with 
the exception of the anterior lymph hearts, is the first lymphatic to 
appear in Bufo embryos, and perhaps most of the anlagen of 
which originate, as has just been described, in connection with 
the endothelium of potential haemal vessels before that endo- 
11 Anyone wishing to follow the controversy regarding the origin of lymphatics 
is referred to the numerous papers which have appeared during the last decade 
in America on the problem of lymphatic development. The larger papers of 
Sabin, Huntington, and McClure on the development of the mammalian lym- 
phatic system contain a comprehensive list of the literature. 
