194 George S. Huntington and Charles F. W. MeClure. 
are of interest on account of their bilateral arrangement as well 
as for the reason that they correspond approximately in their 
position to that of the primary connection which exists at an 
earlier stage between the veno-lymphatic plexus and the base of 
the primitive ulnar vein. If it is true that the sac separates 
temporarily from the venous system, then it is quite natural that 
pictures should be observed during the process of separation 
and before the same is quite completed, which would lead to the 
description of these “‘extremely doubtful’’ connections. 
In a 11 mm. embryo (series 27) in which the jugular lymph sae 
was established, no communication between lymph sac and vein 
could be detected. Two processes of the lymph sac, however, ap- 
proach and almost reach the two points at which the lymph sae 
was formerly connected with the veins. In a former paper we 
have termed these two processes the Jugular and Subclavian 
Approaches, respectively. 
In a 12 mm. embryo (series 78) no communication could be 
detected on the right side. On the left side of the same embryo 
however, the anterior end of the lymph sac was found to be in 
wide-open communication with the internal jugular vein (anterior 
tap of evacuation) but was completely separated from the veins 
at all other points. This condition in an embryo of this age will 
be further considered in connection with another topic. 
In a 18 mm. embryo no communication between lymph sac 
and veins could be detected on either side. 
In a 14 mm. embryo examined by the writers a doubtful 
communication was observed on the left side, situated slightly 
cranial to the jugulo-subclavian junction (series 34, slide 21, sec- 
tion 24). No communication could be detected at the junction 
of the external and internal jugular veins. 
In another 14 mm. embryo (series 37) a-tap was established at 
the common jugular angle, but no connection was found at the 
jugulo-subclavian confluence. 
In the above sense, if the final connections are secondary 
then, in the beginning of their establishment (14 mm.), stages 
might be found which give incomplete and doubtful pictures of 
lymphatico-venous connection when compared with the definite 
and typical arrangement once fully established. 
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