PAKKER 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 con-esponding 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. 



