Frederic T. Lewis 221 
the brain; thence outside of the otocyst, and nerves seven to eleven in- 
elusive, finally becoming internal to the twelfth nerve near the gang- 
lion nodosum. Originally internal to all these nerves, it later becomes 
external to them all (Salzer). 
A yein coming from the side of the tongue passes outside of the 
tenth nerve and enters the internal jugular at the level of the lateral 
thyroid pocket. The corresponding vein from the left side begins in 
the median line, along which it continues a short distance before turn- 
ing to one side. In a 14-mm. pig the right vein is the median one. 
Anastomosis between the two is probable. These vessels, which to my 
knowledge have never been described, are found in 6-mm. pigs, running 
along the dorsal pericardial wall and proceeding from as far forward 
as the second arch. In a pig of 20 mm. the anterior cardinal veins 
have approached so near that the intervening space is less than the 
diameter of one of them. Where they are nearest these transverse 
veins are found, passing ventral to the arteries, dorsal to the cords of 
the thymus, and just caudad from the thyroid, with which they are 
closely connected. Here the very short left innominate vein is formed, 
uniting the anterior cardinals. That part of the right cardinal be- 
tween the anastomosis and the heart subsequently disappears. 
Near the duct of Cuvier the anterior cardinal vein is split for some 
distance, and the subclavian vein arises from its outer part. That sec- 
tion of the external jugular which is near the heart appears to be cut 
off from the internal jugular by the growth of slender mesenchymal 
partitions. After the disappearance of the posterior cardinal vein, the 
right duct of Cuvier becomes a continuation of the internal jugular 
vein, and with the migration of the subclavian vein, adult conditions 
ensue. Shortly before birth, these veins are arranged like a four-tined 
fork, the handle being the vena cava superior (duct of Cuvier and 
anterior cardinal), the inner tines being the internal jugulars (anterior 
cardinals), and the outer tines representing the external jugulars from 
which the subclavians pass off laterally. 
The posterior cardinal veins arise near the tail and enter the Wolffian 
bodies where they become divided into sinusoids (Minot, 00, 1). They 
form distinct trunks as far cephalad as the cross anastomosis between 
the subcardinal veins. This section of the right posterior cardinal be- 
comes a part of the inferior cava, the corresponding portion on the left 
forms a part of left spermatic vein. A prominent anterior trunk 
unites with two others and proceeds to the duct of Cuvier. This sec- 
tion of the posterior cardinal vein loses its connection with the heart 
on the right side, but retains it on the left, forming the hemiazygos 
15 
