No. 6. — The Thoracic Derivatives of the Postcardinal Veins in 

 Swine. By G. H. Parker and C. H. Tozier.^ 



Introduction. 



Although 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 ceUoidin-mass. In the former case the 

 veins were afterwards dissected out ; in the latter, corrosion preparations 

 were made by dissolving away the tissues of the embryo in an artificial 



1 Contributions from the Zoological 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 

 veins, 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 and vena cava anterior, have been replaced by postcava and precava, and it is 

 therefore hoped that they will commend themselves alike to embryologists and 

 comparative anatomists. 



VOL. XXXI. — xo. 6. 



