84 F. W. THYNG 



The extra-cranial part of the right anterior cardinal is repre- 

 sented in the adult by the right internal jugular and innominate 

 veins, and by the part of the superior cava distal to the point of 

 entrance of the vena azygos. 



The extra-cranial part of the left anterior cardinal (plate 5) at 

 this time is symmetrical in size and position with its fellow of the 

 right side. Just before entering the sinus venosus the left com- 

 mon cardinal (V.card.c.s.) turns to the right and occupies the 

 sulcus coronarius on the diaphragmatic surface of the heart. 

 It is shown in the latter situation in plates 1 and 4. 



The vertebral veins of which the right (V.vei'.d.) is recon- 

 structed in plate 4, take the major share in the drainage of the 

 cervical intersegmental veins. They open on either side into the 

 dorsal aspect of the common cardinal near the termination of the 

 azygos and hemiazygos respectively. 



The above description of the extra-cranial portions of the 

 anterior cardinal veins includes only the main venous channels 

 draining the sinuses of the developing dura mater. In the 

 opinion of the author the true 'anterior cardinals' are not repre- 

 sented by these channels alone, but by the m.ain trunks of the 

 vertebral veins as well. This opinion is supported by the occur- 

 rence in a pig embryo of 7.8 mm. (Thyng '11) of a series of fen- 

 estrae in the dorsal portion of the anterior cardinal vein (fig. 2) 

 which appears to foreshadow the segregation of the dorsally 

 placed vertebral vein from the main ventral channel (corre- 

 sponding to the anterior cardinal as described above). A ver- 

 tebral vein, thus formed, would receive the cervical interseg- 

 mental veins as does the vertebral in this embryo. 



The right and left linguo-facial veins (V.ling-fac.) (Grosser 

 '01, Lewis '09, and others) are shown in plates 4 and 5, 

 respectively, and the terminal parts of both are seen in plate 6. 

 Each arises in tributaries from its own side of the tongue, man- 

 dible and face. The trunk, thus formed, enters the ventral wall 

 of the internal jugular vein of its own side, near the p'ace where 

 the latter is crossed medially by the hypoglossal nerve (N.hyp.). 

 Earlier in development each linguo-facial vein enters the ventral 

 wall of the anterior cardinal at a more caudal level, i.e., immedi- 



