PARKER AND TOZIER : POSTCARDINAL VEINS IN SWINE. 143 
3. The united postcardinal and accessory veins of the right side give 
rise to the azygos vein ; those of the left side, to the hemiazygos. 
4, The azygos and hemiazygos veins receive the intercostal veins of 
their respective sides and become mutually connected by several trans- 
verse veins. 
5. The cardinal portion of the azygos vein usually degenerates com- 
pletely, and the right intercostal veins formerly connected with it then 
find an outlet through the corresponding part of the hemiazygos, which 
persists in the adult pig. 
6. The accessory parts of the azygos and hemiazygos veins may re- 
main connected with the cardinal part of the hemiazygos, and by their 
variations give rise to three structural types: first, one in which both 
accessory parts are equally developed ; secondly, one in which the hemi- 
azygos accessory predominates; and thirdly, one in which the azygos 
accessory predominates. 
