298 George 8. Huntington and Charles F. W. McClure. 
The internal jugular vein has relatively decreased in size, while 
the external jugular and cephalic veins have correspondingly 
enlarged. The two divisions of the lymph sac (dorsal and ventral) 
have become closely amalgamated in the caudal portion and the 
united sac is still perforated some distance from its dorsal margin 
by the fifth cervical nerve (S.P.N.V.). The sac terminates 
-audally in four prolongations: 
1. The jugular approach (fig. 61) terminates in a pointed 
extremity, which enters, as previously described, in a wedged- 
shaped invagination, with valve formation, the dorsal aspect of 
the angle of confluence of the internal jugular (precardinal) and 
the combined trunk of the external jugular and cephalic veins. 
This forms the typical secondary and final lymphatico-venous 
tap at the common jugular confluence. (Compare with figs. 1, 
2 and 3 of adult). 
2. The subclavian approach (fig. 61), is a much elongated pro- 
cess of the ventro-caudal end of the jugular sac, which extends 
caudad, ventral to and somewhat beyond the jugulo-subclavian 
junction, where it ends in a pointed blind extremity. A doubt- 
ful point of connection exists with the vein near the jugulo- 
subelavian junction. The subclavian approach is potentially 
in position to establish a typical secondary entrance into the 
dorsal aspect of the jugulo-subelavian angle. We have, therefore, 
probably here an instance in which, while the common jugular 
secondary lymphatico-venous tap is already established, the sub- 
clavian connection has not yet been made. It is, of course, on the 
other hand, possible that we are dealing with an individual which 
in the adult state would. have presented only a single (common 
jugular) lymphatico-venous connection, and in which the secon- 
dary jugulo-subeclavian tap was never formed. (Fig. 1, left side). 
3. The third prolongation is formed by the primitive ulnar 
lymphatic as a blind process of the sac, arching caudad over the 
sixth spinal nerve (fig. 61, S.P.N.VJ.), along the dorsal aspect 
of the subclavian vein. 
4. The point at which in later stages the proximal end of the 
thoracic duct will connect with the jugular sac, is represented 
(fig. 60), by a short process which lies upon the dorsal surface 
