194 THE AMERICAN NATURALIST. [VoL. XXXIV. 
The middle sacral vein usually opens into the left common 
iliac, and this was found to be the case by the writer in 60 per 
cent of the cats examined. In some instances this vein (5) was 
found to open into the left common iliac (2), near the point of 
union of the external and internal iliac veins (3 and 4), Fig. 6. 
In other instances its connection 
with the left common iliac was 
somewhat cephalad of this point. 
In four cats, or 16 per cent of 
those examined, the middle sacral 
vein (5) opened into the right com- 
mon iliac (2), Fig. 8. This was 
the case with one of those prepara- 
tions in which the common iliac 
veins were unusually long and 
joined the single postcava opposite 
the sixth lumbar vertebra. 
In five cats, or 20 per cent of 
those examined, the middle sacral 
vein (5) opened into the angle of 
union of two veins which joined a 
vein of the right and left side, re- 
spectively (Figs. 1, 3, 7). 
4. ON THE PRESENCE OF Fo- 
RAMINA IN VEINS THROUGH WHICH 
ARTERIES AND NERVES Pass. — 
(a) Six cases were met by the 
writer in which a vein presented a 
completely formed foramen through 
which an artery passed. In four 
Fic. 8. — Princeton Morphological -- TT 
seum, No. 606. Perforation of V. a of these cases the internal iliac 
communis dextra by A. iliaca aig 
dextra, Ventral aspect. a. V. iliaca artery passed through a foramen 
communis. 13. mesenterica post. 
3 H TP " 
GM M remaining qum. iN the common iliac vein. In the 
I. 
A D 
bers, sec Fi EET 
ge hue Ris two remaining instances a lumbar 
artery passed dorsad through a foramen in the postcaval vein. 
Two cases were met with in which the right internal iliac 
artery (11) passed through a foramen in the right common 
iliac vein (2), as represented by Fig. 8. 
