AORTA. 



197 



the great sacro-lumbar mass of muscles, in which 

 they are lost, anastomosing frequently with each 

 other, and with the dorsal branches of the low- 

 est intercostal and ileo-lumbar arteries. The 

 continuations or anterior divisions of the lum- 

 bar arteries pass outwards between the psoas 

 and quadratus lumborum muscles, to which they 

 give small branches, as well as to the diaphragm, 

 kidney, renal capsule, and surrounding cellular 

 membrane; they then continue their course 

 forwards between the layers of the abdominal 

 muscles, in company with branches of the lum- 

 bar nerves, and anastomose with the lower in- 

 tercostals, mammary, epigastric, and circum- 

 flexa ilii. 



The middle sacral artery arises from the back 

 part of the abdominal aorta, immediately above 

 the origins of the primitive iliacs, from one of 

 which it arises in some rare cases, it descends 

 exactly over the middle of the anterior surface of 

 the bodies of the last abdominal vertebra, false 

 vertebrae of the sacrum and os coccygis, lying 

 close on the surfaces of those bones ; the 

 branches which it gives off are distributed in 

 a lateral direction ; the first is the largest and not 

 unfrequentlyis the fifth lumbar artery, the size of 

 which sometimes exceeds that of the continuation 

 of the trunk of the middle sacral itself. This 

 branch divides into an anterior and a posterior, 

 the distribution of which is similar to that of 

 the superior lumbar arteries. Two transverse 

 branches usually arise from the middle sacral 

 on the body of each false vertebra ; these pass- 

 ing outwards give branches to the periosteum 

 and the substance of the sacrum, anastomose 

 with branches of the lateral sacral arteries, 

 and enter the anterior sacral foramina, where 

 they give some branches to the origins of the 

 sacral nerves, and emerging from the posterior 

 sacral foramina are lost in the muscles arising 

 from the back part of the sacrum ; finally, the 

 middle sacral terminates at the extremity of the 

 coccyx in small branches, which it sends to the 

 rectum and surrounding fat. 



The middle sacral artery is sometimes found 

 double; in the foetus this artery is propor- 

 tionally larger than in the adult, especially in 

 the earlier periods of gestation. In some ani- 

 mals, the size of the middle sacral artery is 

 scarcely inferior to that of the aorta itself, as 

 in the cetacea and fishes. In all animals fur- 

 nished with tails, the size of this artery bears 

 a constant relation to the size of that member. 



Aneurism rarely affects any of the branches 

 of the aorta above described ; it, however, occa- 

 sionally occurs in the OEliac or mesenteric arte- 

 ries, or some of their branches. An interesting 

 case of aneurism of the hepatic artery unat- 

 tended by pulsation during life, and which 

 produced jaundice by pressing on the ductus 

 communis choledochus, is reported by Dr. Wil- 

 liam Stokes, in the Dublin Journal of Medical 

 and Chemical Science, for July 1834. We 

 once witnessed the dissection of a female aged 

 forty, under the care of the late Professor Todd, 

 in the Surgical Hospital of the House of Indus- 

 try in Dublin, in whom three distinct aneurisms 

 of large size were found in the epigastric region ; 

 one of the hepatic artery, which communicated 



with that vessel by a longitudinal fissure, and 

 which had opened into the cavity of the gall- 

 bladder; one of the trunk of the coronary artery 

 of the stomach, and a third of the splenic 

 artery. A remarkable feature in this case, and 

 that of Dr. Stokes, was the absence of pulsa- 

 tion during life, in consequence of which the 

 nature of the disease was not discovered until 

 the post-mortem examination ; the above cir- 

 cumstance may be attributed to the want of 

 resistance in the surrounding parts, and it is 

 one which frequently obscures the diagnosis 

 of abdominal aneurisms. 



BIBLIOGRAPHY. Diet, de Medecine, art. Aorte. 

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