862 A MANUAL OF ANATOMY 



and beyond that it is placed behind the rectum. On reaching the 

 tip of the coccyx it terminates in the coccygeal body. The branches 

 of the artery are as follows: anterior or recfal to the posterior 

 wall of the rectum, where they anastomose with the superior and 

 middle hemorrhoidal arteries ; lateral to the front of the sacrum 

 and coccyx, which anastomose with the lateral sacral arteries ; and 

 terminal to the coccygeal gland. The vessel occasionally furnishes 

 a fifth pair of lumbar arteries, which wind round the sides of the 

 body of the fifth lumbar vertebra; 



The middle sacral artery represents the caudal aorta of animals, 

 and its lateral branches are serially homologous with the lumbar 

 branches of the abdominal aorta. 



The middle sacral vein is at first arranged as two venae comites, 

 but these subsequently unite to form a single vessel, which usually 

 terminates in the left common iliac vein. 



Coccygeal Gland (Body) of Luschka. — This so-called gland is 

 situated in front of the tip of the coccyx. It is about the size of 

 a small pea, and is composed of a few nodules which are held 

 together and invested by connective tissue. It receives the 

 terminal twigs of the middle sacral artery. In structure it consists 

 of groups of polyhedral cells, united by connective tissue, and 

 permeated by blood-capillaries and sympathetic nerve-filaments. 

 It is similar to the carotid body, which is situated behind the 

 common carotid artery of each side close to its bifurcation. 



Sacral Glands. — This group comprises a few lymphatic glands 

 which lie in front of the sacrum along the middle line, behind the 

 rectum. They receive their afferent vessels from the rectum 

 and upper part of the anal canal, and from the posterior wall of 

 the pelvis, and their efferent vessels pass to the median lumbar 

 glands. 



*Gangliated Cord of the Sympathetic. — ^This is situated close to the 

 inner side of the anterior sacral foramina. The two cords, right 

 and left, converge as they descend, and in front of the coccyx 

 they are connected by a loop which sometimes presents a single 

 median ganglion, called the ganglion impar or coccygeal ganglion. 

 The number of ganglia on each cord is usually four. 



Branches. — (i) Grey rami communicantes, which spring from the 

 ganglia and pass to the anterior primary divisions of the sacral and 

 coccygeal nerves. These rami are very short. (2) Visceral branches, 

 which pass from the upper one or two ganglia to the pelvic plexus. 

 (3) Parietal branches, which are distributed over the front of the 

 sacrum, and which communicate with those of the opposite side, 

 so as to form a plexus upon the middle sacral artery. From 

 the terminal loop and ganglion impar (when present) branches 

 proceed to the front of the coccyx and coccygeal body. The 

 ganglia of the sacral chain do not receive any white rami communi- 

 cantes from the sacral nerves, these, under the name of the pelvic 

 splanchnics, going chiefly to the pelvic plexus. 



Levator Ani — Origin. — (i) The posterior surface of the body of 

 the OS pubis in its lower part, below the attachment of the pubo- 



