200 George 8S. Huntington and Charles F. W. McClure. 
ing upon the developmental stage and individual variation. Of 
these tributaries the one labeled 4 in fig. 8 is the most important, 
not only on account of the extensive drainage area which it con- 
trols, both caudad and cephalad of its precardinal terminal, by 
means of its branches a and b, but also on account of the relations 
which it subsequently maintains with respect to the development 
of the anlages of the jugular lymph sac (caudal division of the 
ventral veno-lymphatic plexus). 
B. Ventral Tributaries of the Caudal or Straight Segment of the 
Precardinal Vein. 
This portion of the precardinal usually receives two main 
branches, frequently joined at their terminal to include a fenestra. 
AREA OF PRE- AND POSTCARDINAL CONFLUENCE. 
3. Jugular Promontory and Duct of Cuvier. 
At the confluence of the pre- and posteardinal veins the main 
venous channel enlarges into a capacious swelling, which gives 
rise ventrally to the duct of Cuvier, while it projects dorsally as a 
rounded protuberance which we have designated as the Jugular 
Promontory. This promontory constitutes an important region 
in the future history of the veno-lymphatic and the definite lym- 
phatic structures. Primarily it develops as the result of the con- 
fluence of large venous trunks. It receives on its ventro-lateral 
aspect the cephalic vein, and ventrally the anlage of the external 
jugular which, after confluence with the cephalic vein, forms a 
trunk of large size entering the ventro-lateral aspect of the promon- 
tory.. The jugular promontory usually receives in later stages 
the three or four well-defined dorsal tributaries (5S, 6S, 7S, and 8S), 
in fig. 8, which enter its convexity along the dorso-medial aspect. 
In the later stages the jugular promontory also receives dor- 
sally the drainage from the body-wall and anterior limb-bud by 
the primitive ulnar vein. The development of this vein will be 
considered under the following topic The Primitive Ulnar Seg- 
ment of the Postcardinal Vein. 
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