THE ARTERIES. 309 



passes onto the lateral surface of the tail, extending caudad 

 along its side. 



1 1. 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 vertebrae. In the caudal region 

 it passes through the haemal arches, covered by the chevron 

 bones. Between the vertebrae it gives offside 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 vertebrae, sacral and caudal. 



The External Iliac and its Branches. The origin of the 

 external iliac (Fig. 126, k] is described above (page 307). 

 It gives off the following branches: 



i . A. profunda femoris (Fig. 126, y\ 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. 



