THE PHREXIC ARTERIES. 435 



aperture along with the vas deferens (i) ; S, inferior mesenteric artery ; 9, lumbar arte- 

 ries : 9', the lowest lumbar artery rising in this instance from the middle sacral (1') ; 

 10, 10', right and left common iliac arteries; 11, 11, placed between the external and 

 internal iliac arteries on each side ; 12, left epigastric artery ; 13, circumflex iliac artery. 



ously between the layers of the broad ligament of the uterus, is guided 

 to the attached margin of the ovary, which it supplies with branches. 

 Some small offsets can be also traced along the round ligament into 

 the inguinal canal, and others along the Fallopian tube : one, continuing 

 inwards towards the uterus, joins with the uterine artery. 



In early foetal Hie the spermatic and ovarian arteries are short, as the testes 

 and the ovaries are at first placed close to the kidneys, but the arteries become 

 leng:thened as these organs descend to their ultimate positions. 



Varieties. — The ycrmatic arteries occasionally arise by a common trunk. Two 

 spennatic arteries are not unfrequently met with on one side ; both of these 

 usually arise from the aorta, though sometimes one is a branch from the renal 

 artery. A case has occurred of three arteries on one side, — two from the aorta 

 and the thii-d from the renal. 



B.— PARIETAL BRANCHES OF THE ABDOMINAL AORTA. 



Inferior phrenic arteries. — The phrenic arteries are two small 

 vessels, which spring from the aorta, either close together or by a short 

 common trunk, on a level with the under surface of the diaphragm. 

 When they arise separately from each other, one is frequently derived 

 from the coeliac artery close to its origin, and the other from the 

 aorta immediately above. They soon diverge from each other, and, 

 passing across the crura of the diaphragm, incline upwards and outwards 

 upon its under surface ; the artery of the left side passing behind the 

 oesophagus, whilst that of the right side passes behind the vena cava. 

 Before reaching the central tendon of the diaphragm, each of the 

 arteries divides into two branches, of which one runs forwards towards 

 the anterior margin of the thorax, and anastomoses with the musculo- 

 phrenic branch of the internal mammary artery, while the other pursues 

 a transverse direction towards the side of the thorax, and communicates 

 with the terminations of the intercostal arteries. 



Branches. — Each phrenic artery gives small branches (superior capsular) to the 

 suprarenal capsule of its own side ; the left artery sends some branches to the 

 oesophagus, whilst the artery of the right side gives off small vessels which reach 

 the termination of the vena cava. Small offsets descend to the liver betAveen the 

 layers of the peritoneum. 



Varieties.— The phrenic arteries are found to vary greatly in their mode of 

 origin, but these deviations seem to have little influence on their course and dis- 

 tribution. In the first place they may arise either separately, or by a common 

 trunk : and it would appear that the latter mode of origin is nearly as frequent 

 as the former. "When the two arteries are joined at their origin, the common 

 trunk arises most frequently from the aorta ; though, sometimes, it springs from 

 the cceliac axis. "When arising separately, the phrenic arteries are given off 

 sometimes from the aorta, more frequently from the coeliac axis, and occasionally 

 from the renal ; but it most commonly happens that the artery of the right side 

 is derived from one, and that of the left side from another of these soui-ces. 

 An additional phrenic artery (derived from the left hepatic) has been met 

 with. 



In only one out of thirty-six cases observed by R. Quain did the phrenic arteries 



F F 2 



