No. 6.— The Thoracic Derivatives of the Postcardinal Veins in 
Swine. By G. H. PARKER and ©. H. TozıEr.! 
Introduction. 
Auruovan the postcardinal veins? in swine were originally studied by 
Rathke, and have since been reinvestigated by Hochstetter, our knowl- 
edge of them is admittedly fragmentary ; for Hochstetter himself regrets 
that his results in the main do little more than raise doubt as to the 
accuracy of some of the most important of Rathke’s statements, without 
giving grounds enough for full criticism. It is our purpose in this paper 
to present what seems to us a consistent account of the changes that 
these veins undergo, and to offer some critical comments on the ques- 
tions raised by Hochstetter. 
In dealing with this subject we have had recourse to the two general 
methods of serial sections and injection. The smaller embryos were 
cut into serial sections, and the courses of the veins then studied by a 
simple method of graphic reconstruction. The larger ones were injected 
with a raw starch-mass, or a celloidin-mass. In the former case the 
veins were afterwards dissected out; in the latter, corrosion preparations 
were made hy dissolving away the tissues of the embryo in an artificial 
1 Contributions from the Zoólogical Laboratory of the Museum of Comparative 
Zoology at Harvard College, E. L. Mark, Director, No. LXXXVII. 
2 Some little confusion exists as to the terminology of the principal veins in 
lower vertebrates and the homologues of these veins in mammalian embryos. The 
principal veins from the head of a fish are usually designated by comparative 
anatomists as right and left anterior cardinal veins, and their homologues in the 
mammalian embryo are generally named by embryologists right and left jugular 
veins. For these veins, whether they be in the adult fish or in the embryonic 
mammal, we propose to use the names right and left precardinals. In a similar 
way, the blood-vessels designated by comparative anatomists as right and left 
posterior cardinal veins, and by embryologists simply as right and left cardinal 
voins, will be called by us right and left postcardinals. These changes are in 
harmony with those by which the longer and older names, vena cava posterior 
and vena cava anterior, have been replaced by posteava and precava, and it is 
therefore hoped that they will commend themselves alike to embryologists and 
comparative anatomists. 
VOL. XXXI. — NO. 6. 
