Development of the Jugular Lymph Saces. 245 
part of the terminal of the early branch 4 ina more advanced state 
of development. It has retained a cephalic connection with the 
precardinal (X, fig. 33), but the para-precardinal channel has 
broken away at the usual distal tap (at B) into the angle between 
the precardinal and promontory, apparently by secondary fusion 
at this point with the dorsal veno-lymphatic plexus. 
This embryo may possibly offer the ontogenetic explanation of 
the adult cases in which the lymphatic system, through the Jugu- 
lar lymph sac, communicates with the venous system only at 
the distal of the two customary taps, viz., at the jugulo-subclavian 
angle. By early union of the elements of the vencral veno- 
lymphatic plexus with the dorsal plexus, the terminal of the 
latter, at the jugulo-subclavian angle, may lead secondarily to the 
formation of the only definite adult lymphatico-venous portal. 
As previously stated (p. 192) the results of this investigation 
oblige us to assume that the early embryonic connections of the 
veno-lymphatic plexuses with the permanent veins are given up 
and that the adult lymphatico-venous taps are formed secondarily. 
Compared with series 109 (figs. 27 and 30) this side of the 
embryo clearly shows the double character now assumed by pre- 
cardinal tributary 4 and the associated para-precardinal channel 
(figs. 833 and 34), and the lines along which the veno-lymphatie 
and dorsal somatic components separated. On the left side of this 
embryo this separation is complete, except at one point (figs. 33 
and 34, A) where the original connection between the two still 
‘persists. 
The veno-lymphatic component of 4 (4VL in fig. 33) and its asso- 
ciated para-precardinal channel is expanded and dilated. It has, 
as in series 199 (figs. 27 and 30), retained its original point of 
connection with the precardinal vein (X in fig.33). The promon- 
torial opening of the para-precardinal channel at the promontorio- 
precardinal angle has been much reduced, owing perhaps to the 
dorsal extension of the fenestra Y. (fig. 33), resembling somewhat 
the condition found in series 109 (fig. 30). The small curved 
tributary B in fig. 33 at the promontorio-precardinal angle, prob- 
ably represents a portion of the para-precardinal channel separated 
from the main vessel by the extension of fenestra Y. The veno- 
