No. 10.— On the Veins of the Wolffian Bodies in the Pig. 
By Charles Sedgwick Minot. 
In transverse sections of pig embryos of 10 mm. and upwards in 
length, representing stages in which the Wolffian bodies (Meso¬ 
nephroi) are well developed, no cardinal veins can be distinguished 
on the dorsal side of the Wolffian bodies. As we rely principally 
upon pig embryos for the class work in embryology at the Harvard 
Medical School, it was important to elucidate the history of the 
cardinal veins. During this undertaking I found certain relations 
of the veins, which seem to me worthy of description and illustration. 
The material studied consists of twenty-live series of sections of 
pig embryos of from 6.0-24.0 mm. in length, corresponding in range 
approximately to Figs. 14-29 inclusive of Keibel’s Normentafeln I. 
Embryos of 12.0 mm. were found to be especially instructive as 
regards the transformation of the cardinal veins, and accordingly 
the following descriptions are based chiefly on that stage. To 
render verification of the observations feasible, the sections are 
referred to by the number of the series, and the number of the 
section in the series. For example, Fig. 3 is taken from iSeries 6, 
section 423. The collection is the property of the Harvard Embry- 
ological Laboratory and is open to qualified investigators. 
In pig embryos of 12.0 mm. the cardinal vein is a large stem, 
which may be said to end abruptly at the cephalic end of the Wolf¬ 
fian body, Fig. 1, although a prolongation of small caliber may 
sometimes be traced a short distance on the dorsal side of the body. 
The vena cava inferior is a large vessel a little to the right of the 
median line, Fig. 3, and receives its blood almost exclusively from 
the Wolffian bodies. The primitive kidneys have at this stage two 
large veins. The renal and iliac branches of the cava inferior 
commence their development in slightly older embryos. The left 
umbilical vein is a large blood channel, Fig. 5, which passes from 
the umbilicus, directly through the liver to the heart; it has numer¬ 
ous side branches in the liver. The right umbilical vein is markedly 
smaller than the left; in series 5 (transverse sections) it has a wide 
connection inside the liver with the portal vein; in series 6 (sagittal 
