MINOT: VEINS OF THE WOLFFIAN BODIES IN THE PIG. 2G7 
of the organ of Girald&s (Paradididymis, Paroophoron). Unfor¬ 
tunately, I have not been able to follow the further history of these 
parts, so that the homologies indicated must be left for future inves¬ 
tigations to verify or deny. 
The mesonephric branches from the end of the cava inferior abut 
partly directly upon the Wolffian tubules, and partly indirectly, 
since they are each continued by a headward or upper and a tail- 
ward or lower branch, as illustrated in the reconstruction, Fig. 5. 
These branches lie upon the dorsal side of the organ and take an 
arching course. They were originally portions of the cardinal veins, 
and their connection with vena cava inferior is secondary. This 
change in the connections of the distal parts of the cardinal veins 
was described by Rathke long ago, 30 . 1 , 38 . 3 , and has been studied 
more recently by Hoclistetter, 87 . 2 , 88 . 1 , 88 . 3 , 92 . 1 , 92 . 3 , 93 . 1 , 
94 . 3 , 97 . 2 , and Zumstein, 96 . 1 , 97 . 1 . I must point out that the 
diagram given by O. Hertwig in his Entwickelungsgeschichte, 
Ftinfte Auffiage, p. 537, and which I have reproduced in my Human 
Embryology, p. 543, represents the transformations of the veins 
incorrectly. It is incorrect especially in failing to show that each 
cardinal vein becomes discontinuous, and that the caudad segment 
of the cardinal vein becomes connected near its own middle with 
the end of the vena cava inferior, so that this segment is trans¬ 
formed into what appear as the two branches of the mesonephric 
vein. This change of connection is so important that the vessels of 
the new arrangement deserve a special name, and I propose there¬ 
for the term mesonephric vein (vena mesonephrica ). The trunk 
of this vein is a new connecting stem established between the end of 
vena cava inferior and the cardinal vein; the two main branches 
of the vein are the remnants of the caudad division of the cardinal 
vein, and they may be conveniently styled the superior and inferior 
branches respective^, the superior being that lying nearest the head. 
The Wolffian body of the pig is then remarkable for being fur¬ 
nished with two very large veins, both receiving their blood supply 
practically exclusively from the Wolffian body. It seems possible 
that this peculiar condition, which does not obtain in Guinea pigs 
or in man, is connected with the great functional activity of the 
mesonephros in the ungulates, which develop an enormous allantoic 
sack and fill the sack with a urinary excretion. Guinea pigs have a 
small, man a minimal allantois, and it must be assumed that the 
mesonephric functions are correspondingly reduced. As regards 
