8o6 HUMAN ANATOMY. 



those of the right side also pass beneath the inferior vena cava, while the two upper 

 ones of the same side pass beneath the receptaculum chyli. They then pass beneath 

 the psoas muscle and the branches of the lumbar plexus, the two upper ones also 

 passing beneath the crura of the diaphragm ; and then, farther out, they pass beneath 

 the quadratus lumborum, except in the case of the last pair, which lies upon the ante- 

 rior surface of that muscle. At the outer border of the quadratus they pass between 

 the transversalis and the internal oblique muscles of the abdomen, and are continued 

 onward in the abdominal wall, eventually piercing the internal oblique and reaching 

 the rectus muscle. 



Branches. — The lumbar arteries are to be regarded as continuations of the series of inter- 

 costal vessels, and, like the thoracic members of the series, each gives off a dorsal branch (ramus 

 dorsalis). This arises when the vessel lies behind the psoas muscle and is directed posteriorly, 

 soon dividing into {a) a spinal branch (ramus spinalis), which enters the spinal canal through 

 the intervertebral foramen and anastomoses with the anterior and posterior spinal arteries ; and 

 {d) a muscular branch, which is distributed to the muscles and skin of the back. In addition, 

 each lumbar artery gives off numerous branches to the muscles with which it comes into relation. 



Variations. — One or more of the lumbar arteries may be wanting and two or more of them 

 may arise by a common stem. 



9. The Middle Sacral Artery. — The middle sacral artery (a, sacralis media) 

 (Fig. 718), which is to be regarded as the continuation of the abdominal aorta, is 

 a small vessel arising from the posterior surface of the aorta immediately above its 

 bifurcation into the two common iliacs. It passes downward in the median line over 

 the last two lumbar, the sacral and the coccygeal vertebrae, and terminates opposite 

 the tip of the coccyx by sending branches to the coccygeal body or Luschka's gland 

 (glomus coccygeum). 



Branches. — It sometimes gives rise to a fifth pair of lumbar arteries (aa. lumbales imae), and 

 lower down it sends off small lateral branches which send branches inward to the spinal canal 

 through the anterior sacral foramina and anastomose with the lateral sacral branches of the 

 internal iliac artery. These lateral branches appear to represent a continuation of the inter- 

 costal and lumbar series of arteries, the branches which enter the anterior sacral foramina cor- 

 responding to the dorsal branches of those vessels. 



Variations. — The middle sacral occasionally arises from one or other of the common iliac 

 arteries, and it may give origin to an accessory renal artery. 



Practical Considerations. — Some of the branches of the abdominal aorta, 

 including the splenic, hepatic, renal, superior and inferior mesenteric, and the ovarian, 

 have been the subject of aneurism. 



These aneurisms do not usually attain any great bulk, seldom exceeding the 

 size of a hen's egg. They are apt to be round or oval in shape. Occasionally — espe- 

 cially in the aneurisms of the renal artery — they may almost fill the abdominal 

 cavity. Except when connected with the hepatic, the renal, or the coeliac axis, they 

 are movable, changing their position in the various movements of the body. They 

 may possess also the characteristics of pulsation and bruit. When the coeliac 

 artery is aflfected the disease cannot be distinguished from aneurism of the parent 

 trunk. 



In cases of implication of the hepatic artery, the pressure-effects of the tumor 

 give rise to pain in the right side and to jaundice from obstruction of the hepatic, 

 cystic, and common bile-ducts (Agnew). 



The renal artery has been found to be aneurismal in a small number of instances, 

 the majority being of traumatic origin. The chief symptoms have been: (a) tumor, 

 varying in size, situated in the region of the kidney, immovable with respiration or 

 with change of posture, and almost always without impulse or bruit, on account prob- 

 ably of the usual disproportion, in renal aneurisms, between the large aneurismal 

 cavity and the size of the vessel involved ; (<^) hcsniaturia often but not invariably 

 present ; (r) pain elicited by pressure, or felt in the loin or extending to the genitalia, 

 and sometimes accompanied by retraction of the testis. 



