198 George 8. Huntington and Charles Ff. W. McClure. 
Precardinal area 
1. Arched Portion or Cephalic Arch of the Precardinal 
Vein 
2. Caudal or Straight Segment of the Precardinal Vein 
Area of Pre- and Postcardinal Confluence and of Postcardinal Veins 
3. Jugular Promontory and Duct of Cuvier 
4. Primitive Ulnar Segment of Posteardinal 
The definite connections between the fully developed lymphatic 
and venous systems in later embryonic stages and in the adult fall 
within these districts and occupy normally two typical and, within 
certain limits, constant points: 
1. Common jugular tap: At the angle of confluence of 
internal and external-jugular veins. 
2. Jugulo-subclavian tap: At the jugulo-subclavian angle 
of confluence. 
PRECARDINAL AREA. 
1. The Cephalic Arch of the Precardinal Vein. 
The precardinal vein begins as a strongly curved intracephalic 
arch receiving a number of dorsal tributaries along its convexity 
and a number of branches along its concavity. 
A. Dorsal Tributaries of the Cephalic Arch. 
The dorsal tributaries entering the cephalic arch along its 
convexity vary in number and in mutual relations in individual 
embryos 22.4 in embryos of closely related stages. 
One large tributary of this group (A—B in the schematic figs. 
8 to 16) is uniformly present and in later stages forms the direct 
continuation of the caudal or straight segment of the precardinal 
vein. . 
In addition to this large tributary a number of smaller secondary 
dorsal tributaries of the cephalic arch may be encountered both 
cephalad and caudad of this main vessel (fig. 8, a’, b’, ete.). 
