180 George 8S. Huntington and Charles F. W. McClure. 
develop in conjunction with the main venous channels and their 
tributaries, as well as the variable manner in which they fuse 
together. On account of the large number of reconstructions (71), 
which we have made of the region in which the jugular lymph 
sac is developed, we feel, however, that we are able to present a 
fairly accurate account of all stages of their development. 
Our observations have been based wholly upon the study of 
wax reconstructions made after a slight modification of the method 
of Born. The method of plastic reconstruction was alone used 
by us for the reason that we found it the only one by means of 
which it was possible to get every vascular element in the recon- 
struction and to establish thereby a graded series of stages, 
complete in all details, in which the vascular elements could 
be studied and compared in their proper relations. Moreover, in 
view of recent publications on the vascular system, it is necessary 
to point out the self-evident fact that the only other available 
extra-vitam method of studying the development of vascular ele- 
ments, viz., by injection, will, if successful, only demonstrate 
channels or spaces actually continuous with each other at the time 
of the injection, but will completely fail in revealing vascular 
spaces as yet independent of those injected, although subse- 
quently a connection between the two may be established.’ 
We concluded at the beginning of our investigation that the 
method of injection would prove inadequate as a means of deter- 
mining the actual mode of origin of the anlages of the jugular lymph 
sacs. That our conclusion was correct or not, the reader may best 
judge for himself. 
Most of the embryos studied by the writers were fixed in 
Zenker’s fluid and the sections then stained on the slide with De- 
lafield’s haematoxylin and Orange G. For fixation of tissues and 
differentiation of vascular structures, this method has proved 
most satisfactory. 
Opposite is a list of the cat embryos studied and in part re- 
constructed by the writers in connection with this investigation. 
“See figs. 1 and 2in Dr. Sabin’s paper on The Lymphatic System in Human 
Embryos. The American Journal of Anatomy, vol. 9, 1909, page 64. 
