302. George S. Huntington and Charles F. W. McClure. 
the nerves pass, is broken by reduction of its anterior extrem- 
ity. The lymph sae now is continued cephalad into two 
processes, a smaller ventral and larger dorsal. The former, which 
accompanies the internal jugular vein, becomes further reduced 
and recedes caudad, thus freeing the nerves and allowing them to 
pass between the internal jugular vein and the larger dorsal pro- 
cess which remains as the main component of the lymph sae in 
this stage. 
Series 36, 17°" Embryo 
Reconstruction of left side, 
Dorso-lateral aspect, fig. 63 
The general composition of the caudal end of the jugular lymph 
sac, which is alone represented in the figure, corresponds quite 
closely to the 16 mm. stage. 
A lymphatico-venous connection, as in the 16 mm. embryo, has 
been established on the dorsal aspect of the common jugular con- 
fluence (common jugular tap) by the jugular approach. This tap 
cannot be seen from the dorsal view of the reconstruction but its 
relative position is indicated by a plus sign (+) in the figure. 
The jugular sac is prolonged caudad into a subclavian approach 
which now bifureates near the jugulo-subclavian junction into a 
dorsal and ventral division. The ventral division constitutes the 
caudal extension of the original subclavian approach of the pre- 
ceding stages and in the present embryo communicates ventrally 
with the veins at the jugulo-subclavian junction (jugulo-subclay- 
ian tap). The dorsal division, not present in the 16 mm. embryo, 
extends caudad for a short distance on the dorsal aspect of the 
jugulo-subclavian angle where it ends blindly. It is now in a 
position, however, to establish the secondary dorsal lymphatico- 
venous connection at this point which is frequently met with in 
the adult. 
The thoracic duct is represented by a more complex system of 
vessels in this embryo than in the 16 mm. stage. A number of 
vessels from the thoracic region converge to form a single trunk 
which unites with the jugular sac dorsal to and slightly in front 
of the common jugular tap. The relations of the thoracic duct 
