558 THE BLOOD-VASCULAR SYSTEM. 



the opposite side, and with the musculo-phrenic and comes nervi phrenici, branches 

 of the internal mammary. The external branch passes toward the side of the 

 thorax and inosculates with the intercostal arteries. The internal branch of the 

 right phrenic gives off a few vessels to the inferior vena cava, and the left one 

 some branches to the oesophagus. Each vessel also sends capsular branches to 

 the supi'arenal capsule of its own side. The spleen on the left side and the liver 

 on the right also receive a few brandies from these vessels. 



The Lumbar Arteries, 



The lumbar arteries are analogous to the intercostal. They are usually four 

 in number on each side, and arise from the back part of the aorta, nearly at right 

 angles with that vessel. They pass outward and backward, around the sides of 

 the body of the lumbar vertebra, behind the sympathetic nerve and the Psoas 

 magnus muscle, those on the right side being covered by the inferior vena cava, 

 and the two upper ones on each side by the crura of the Diaphragm. In the 

 interval between the transverse processes of the vertebrae each artery divides into 

 a dorsal and an abdominal branch. 



The dorsal branch gives off, immediately after its origin, a spinal branch, which 

 enters the spinal canal ; it then continues its course backward between the trans- 

 verse processes, and is distributed to the muscles and integument of the back, 

 anastomosing with the similar branches of the adjacent lumbar arteries and with 

 the posterior branches of the intercostal arteries. 



The spinal branch enters the spinal canal through the intervertebral foramen, 

 to be distributed to the spinal cord and its membranes and to the bodies of the 

 vertebrae in the same manner as the lateral spinal branches from the vertebral 

 (see page 521). 



The abdominal branches pass outward, having a variable relation to the 

 Quadratus lumborum muscle. Most frequently the first branch passes in front 

 of the muscle and the others behind it ; sometimes the order is reversed and the 

 lowest branch passes in front of the muscle. At the outer border of the Quadratus 

 they are continued between the abdominal muscles, anastomose with branches of 

 the epigastric and internal mammary in front, the intercostals above, and those of 

 the ilio-lumbar and circumflex iliac below. 



The Middle Sacral Artery. 



The Middle Sacral Artery is a small vessel, which arises from the back part of 

 the aorta just at its bifurcation. It descends upon the last lumbar vertebra, and 

 along the middle line of the front of the sacrum, to the upper part of the coccyx, 

 where it anastomoses with the lateral sacral arteries, and terminates in a minute 

 branch, which runs down to the situation of the body immediately to be described as 

 'Luschka's gland." From it branches arise which run through the meso-rectum 

 to supply the posterior surface of the rectum. Other branches are given off on 

 each side, which anastomose with the lateral sacral arteries, and send off small offsets 

 which enter the anterior sacral foramina. 



The artery is the representative of the caudal prolongation of the aorta of 

 animals, and its lateral branches correspond to the intercostal and lumbar arteries 

 in the dorsal and lumbar regions. 



Coccygeal Gland, or Luschka's Gland. Lying near the tip of the coccyx in a 

 small tendinous interval formed by the union of the Levator ani muscles of each 

 side, and just above the coccygeal attachment of the Sphincter ani, is a small 

 conglobate body about as large as a lentil or a pea, first described by Luschka. 1 

 and named by him the coccygeal gland. Its most obvious connections are with the 

 arteries of the part. 



Structure. It consists of a congeries of small arteries with little aneurisnial 

 dilatations derived from the middle sacral and freely communicating with each 



1 Der Hirnanhany und die Steissdruse dea Menscken, Berlin, 1860 ; Anatomic des Menschen, Tiilungen, 

 1864, vol. ii. pt. 2, p.' 187. 



