THE ARTERIES. 309. 
passes onto the lateral surface of the tail, extending caudad 
along its side. 
11. A. sacralis media (Fig. 126, o).—This is the continua- 
tion of the aorta into the sacral and caudal regions. It-extends 
to near the end of the tail, lying in the ventral middle line 
against the sacral and caudal vertebre. In the caudal region 
it passes through the hazmal arches, covered by the chevron 
bones. Between the vertebrz it gives off side branches com- 
parable to the intercostal and lumbar arteries of the aorta. 
Branches of the sacralis media: 
a. A. sacralis lateralis.—Behind the first sacral vertebra 
a large branch, the lateral sacral, is given off on each side. 
This enters the first anterior sacral foramen, gives a branch to 
the structures in the sacral canal, and sends a dorsal branch 
out through the posterior sacral foramen to the muscles on the 
dorsal side of the sacrum. 
Similar but smaller branches are given off between the suc- 
ceeding vertebre, sacral and caudal. 
The External [hac and its Branches.—The origin of the 
external iliac (Fig. 126, #) is described above (page 307). , 
It gives off the following branches: 
1. A. profunda femoris (Fig. 126, v).—This is given off just 
before the external iliac leaves the abdominal cavity. It passes 
caudad, and about one centimeter from its origin it gives off 
three branches, sometimes all separately, sometimes two in 
common. One of these passes mediad in the lateral ligament 
of the bladder and ramifies on the lateral surface of that organ, 
A second passes through the abdominal wall and into the fat 
on the medial surface of the thigh; it sends a branch caudad 
toward the external genital organs, while its main trunk passes 
distad in the subcutaneous fat almost to the knee. From one 
of these two a small branchlet passes in the male to the sper- 
matic cord and accompanies this to the testis; it represents 
thus the external spermatic artery. The third branch, 
A. epigastrica inferior, passes directly to the ventral surface of 
the rectus abdominis muscle, on which it passes craniad, sending 
branches to the muscles of the abdominal walls. It anasto-: 
moses with terminal branches of the internal mammary artery. 
