(= Yor d 
Development of the Jugular Lymph Sacs. Pir 
tary 1 (fig. 48, 1VL) as many as sixteen of these connections are 
met with along the precardinal vein and the promontory. 
FULLY DEVELOPED VENO-LYMPHATIC STAGE. 
Series 101, 10” Embryo 
Series 77, 11°” Embryo 
Series 101 is characterized by enormous cephalic extension of 
the dorsal veno-lvmphatice plexus, which, as a minutely fenes- 
trated multilocular sac, extends forward to the level of the ceph- 
alic arch of the precardinal. 
The two main divisions of the ventral veno-lymphatic plexus 
are well differentiated, but still entirely separate from each other 
and from the dorsal plexus. 
Series 101, 10°” Embryo 
Reconstruction of left side, 
Lateral aspect, fig. 49 
The group of veno-lymphatics which constitutes the cephalic 
division of the ventral veno-lymphatic plexus, derived from the 
precardinal tributaries 1, 2 and 3, is represented by two indepen- 
dent dilated sacs both of which still retain a connection with the 
precardinal. The united trunk of the first and second spinal 
nerves (SP.N.J and JJ) passes ventro-laterad between the ceph- 
alic of these two sacs and the precardinal, while the third nerve 
(SP.N.IIT) passes between the caudal sac and the dorsal veno- 
lymphatic arch. 
The caudal division of the ventral veno-lymphatic plexus is an 
irregular-shaped sac which lies upon the lateral surface of the pre- 
cardinal and promontory. It communicates with the venous sys- 
tem at only one point (Tap B), by a wide orifice situated on the 
lateral surface of the promontory near the promontorio-precard- 
inal angle. This sac must be regarded as representing a further 
development of the para-precardinal channel and the associated 
veno-lymphatic component of precardinal tributary 4. 
In conformity with a greater degree of veno-lymphatic develop- 
ment, the caudal division of the ventral plexus has given up its 
