Frederic T. Lewis 109 
The jugular sac on the left side, except for an extensive rupture, does 
not connect with the vein. On the right, a pore is found leading from 
the sac to the internal jugular vein near its union with the external, but 
this also may be artificial. ‘Thus in all the series of rabbits no bilateral 
communication of the lymphatics and veins, in the position of the adult 
openings, could be found. The pores, sometimes detected in various 
positions, are not adequate to empty the large sacs, and may indeed be 
artifacts. Communication with the veins in these stages must be by 
osmosis, therefore, and the permanent outlets of the lymphatic system 
must develop later. 
The left jugular sac in Fig. 8 connects with the thoracie duct, which 
arises from a plexus of lymphatics surrounding the aorta. Ventral to the 
aorta these vessels receive the lymphatics from. the mesentery. ‘There are 
none in the leg. The body wall is supplied by those which follow the 
external mammary vein in its anastomosis with the superficial epigastric, 
and by vessels accompanying the ilio-lumbar vein. The ilio-lumbar vein 
of Krause, which Hochstetter named the posterior transverse lumbar, 
supplies the subcutaneous tissue of the back, and seems to be inversely 
homologous with the much larger subscapular vein. At the position 
1. n., indicated in Fig. 8, a node is found among the lymphatics accom- 
panying this vein. A similar node exists on the opposite side, and the pair 
was identified in a duplicate series of a 20-day rabbit. These superior 
inguinal nodes (Krause) develop almost simultaneously with the sub- 
scapular nodes already described. The early appearance of the inguinal 
nodes further identifies the lymphatics of the ilio-lumbar vein with the 
“posterior lymph heart” of Prof. Sabin. It is my opinion that an 
identification of this structure with the amphibian or avian lymph heart 
is, at present, not justified. The posterior heart of the bird empties into 
the coccygeal veins (Sala), and that of the frog into the transverse iliac 
vein, a vessel connecting the femoral with the sciatic vein (Gaupp). The 
ilio-lumbar vein is more anterior than either. Its lymphatics do not differ 
in form, from those accompanying other veins, and they are presumably 
non-contractile. If the first lymph nodes can be utilized in making com- 
parisons, then this “ posteriar heart ” of the rabbit should be compared 
with the lymphatics of the subscapular vein, and not with the jugular sae. 
The jugular sac itself does not empty into the vertebral vein, lke the 
anterior heart of the frog. It is non-contractile, so far as known. If it 
shall be found that the anterior heart of the frog develops from the first 
lymphatics which are formed in that animal, a comparison between the 
jugular sac and a lymph heart may be possible. At present it is not 
evident that mammals possess any lymph hearts. 
