220 George 8. Huntington and Charles F. W. McClure. 
cases, the sac empties itself chiefly, if not entirely, through one of 
the anterior connections (one or two of the primary dorsal somatic 
tributaries) into the cephalic end of the straight segment of the 
precardinal, or even that a secondary connection is established 
between the anterior end of the veno-lymphatic sac and the poste- 
rior extremity of the cephalic arch (through b,! ete., fig. 8), for the 
purpose of serving as a portal through which the blood-contents 
of the sac are poured into the permanent venous channels. (Com- 
pare p. 290, description of series 78, 12m). 
We have designated the connections thus longest retained be- 
tween the veno-lymphatic sae and the veins, as the “‘ taps of evacu- 
ation,’ because, after the sac is fully formed, they serve the pur- 
pose of draining the blood contained in the sac, during the earlier 
periods, into the permanent venous channels, so that after comple- 
tion of this process the sac appears entirely empty of blood, lined 
by endothelium, continuous through the taps of evacuation, 
with the intimal lining of the large veins. 
As the process of evacuation takes place with great rapidity 
there is some difficulty in ascertaining, in individual cases, the 
exact point at which it occurs. The taps of evacuation apparently 
enlarge very much at this time, and, when the process is completed, 
as rapidly close. It is therefore necessary to examine numerous 
stages during this very short and evanescent period in order to 
establish the actual conditions. 
After the evacuation is completed the now fully organized 
lymph sae separates, in the cat embryo, apparently completely 
for a short time from the adjacent veins, by breaking away at the 
evacuating point or points (fig.-16). This closed sac subse- 
quently establishes two sets of secondary connections (fig. 17): 
(a) With the independently formed systemic lymphatics. 
(b) With the venous system. 
These latter connections are normally formed at the two points 
at which the primitive promontorial connections are, inthe major- 
ity of instances, longest retained, viz., at the common jugular 
confluence (common jugular permanent tap) and the jugulo- 
subclavian angle (jugulo-subelavian permanent tap, fig. 17, and 
