THE LYMPHATIC SYSTEM OF THE RAT 
321 
In the inferior vena cava there is a larger percentage of com- 
munications shown. The writer is confident that this connec- 
tion has been overlooked by him in many injections, because of 
either a complicated net-work of vessels between the two lum- 
bar nodes, thus masking the connection, or in instances where 
the plexus was slight, by the communication being directly 
from the node and thus taken for a ruptured vein and not a 
lymphatic vessel. By careful dissection and observation this 
lymphatic communication has been demonstrated in about one- 
half of the specimens used since the first connection was noticed. 
Instances have been noticed where the mass left the main lym- 
phatic channel and entered the vein by one or more taps, giv- 
ing again undoubted evidence of the connection. 
There is no correlation between the number and position of 
the venous communications in any one specimen. All connec- 
tions may be present in one specimen, while only three or two 
or even just the jugulo-subclavian taps may be present in 
others. 
The significance of these venous communications and their vari- 
ability can be explained only after a thorough embryological 
investigation has been made. A¥hefher they can be explained 
most satisfactorily by the sprouting theory, which is advanced 
by Dr. F. R. Sabin, as representing the original points of 
origin, or whether these taps represent later connections of the 
lymphatic system with the venous system, constitutes the prob- 
lem now under investigation. 
Grateful acknowledgment is made by the writer to Professor 
G. L. Houser and Dr. F. A. Stromsten for timely suggestions 
and helpful criticism. 
Laboratories of Animal Biology, 
The State University. 
21 
