No. 399.] FREQUENCY OF ABNORMALITIES. 189 
two posterior cardinals unite with the common postcava oppo- 
site the third lumbar vertebra, the middle sacral vein (V. sacra- 
lis media) opens into the angle of union of two veins which, as 
in that case previously mentioned (Fig. 2), join, respectively, 
Dextra 
o. deg; ntral aspect are inalis 
sinistra SREE: ex sp T. iliaca 
communis sinistra present. 2. V. iliaca 
communis. For remaining numbers, see 
Fig. 1. 
veins of the right and left 
IG 
Venn aspoet V. cardinali deca asinine ge 
padina P dn communis gei. va In addition to the above 
>. V. iaca communis. 13. A. mesenterica post. mode of union, which 
g TET seems to be characteris- 
tic for the middle sacral vein, whenever both posterior 
cardinals unite in the neighborhood of the kidneys, the 
middle sacral vein again opens into the right post-cardinal by 
an additional vessel. This third vessel, Figs. 3, 5 (2, sinistra), 
extends between that portion of the middle sacral vein which 
Opens into the left posterior cardinal and the right posterior 
cardinal vein. It opens into the latter, opposite the point where 
For 
