534 Wisconsin Acadeiny of Sciences, Arts, and Letters. 
artery to the right thymus gland were made out in only three 
specimens and were exceedingly small. 
The glands of this region become very small during star¬ 
vation. In some specimens the thyroid became colorless and 
transparent. The fact that the fat body of the neck had been 
entirely absorbed and that the neck glands had been so much 
reduced may account for the smallness of the blood vessels in 
this region. It is noted elsewhere in this paper that the veins 
of the oviducts are larger while the oviducts are filled with eggs. 
It seems that the size of the blood vessels varies somewhat with 
their activity. 
FIG. 1. 
The left jugular vein. A, aorta; AV, X, remains of the left azygous 
vein; C, carotid artery; E, esophageal veins; EA, esophageal artery 
from thyroid artery; EV, epigastric vein; F, vein from fat body; LT, 
left thymus gland; RJ, right jugular vein; T, thyroid gland; TA, thy¬ 
roid artery; TV, tracheal vein; V, ventricle; VA, vertebral artery. 
The vertebral artery leaves the right aortic arch and runs for¬ 
ward about half way to the head before passing into the mid¬ 
line of the dorsal parietes. In two specimens it sent eight 
branches to the mid-line of the dorsal parietes; in one specimen 
seven; in eight specimens six; in five specimens five; and in 
one specimen only three. These variations were apparently not 
correlated with variations in the external anatomy. The twigs 
from the vertebral artery to the esophagus were very small. Six 
were counted in one specimen. In some specimens they could 
not be made out at all. 
The Dorsal Aorta and Its Branches 
As in other snakes the aorta originates just posterior to the 
heart from the junction of the two aortic arches, (Pig. 1). In 
the eighteen specimens examined the right arch gave off one or 
two intereostals to the mid-line of the dorsal parietes before unit- 
