THORAX AND ABDOMEN OF THE HORSE 175 



examined during the dissection of the pelvic limb, (c) The lateral 

 ventral artery of the tail (a. caudalis lateralis ventralis) continues 

 the original direction of the lateral sacral and thus reaches the tail, 

 where it runs between the inter-transverse and lateral ventral sacro- 

 coccygeal muscles. Between the second and third (or third and 

 fourth) coccygeal vertebrae it gives off the lateral dorsal artery of 

 the tail (a. caudalis lateralis dorsalis) which runs in the cleft between 

 the inter-transverse and the lateral dorsal sacro-coccygeal muscles. 

 (d) From either the right or left lateral sacral or a lateral caudal 

 artery a single (unpaired) coccygeal artery (a. coccygea) takes origin. 

 This follows the middle line of the tail between the recto-coccygeal 

 muscles, and afterwards between the two medial ventral sacro- 

 coccygeal muscles. Not infrequently the coccygeal artery is formed 

 by the union of branches of both lateral sacral arteries. 



(4) A. iliolumhalis. — The ilio-lumbar artery leaves the common 

 point of origin of the cranial gluteal and obturator vessels and runs 

 in a lateral direction, between the transverse process of the first 

 sacral vertebra and the ala of the ilium on the one hand and the 

 ilio-psoas muscle on the other. It supplies branches to this muscle, 

 and, close to the coxal tuber, ends in the middle gluteal and tensor 

 fasciae latae muscles. 



(5) A. glutcea cranicdis. — The large cranial gluteal artery at once 

 passes through the greater sciatic foramen and is found during the 

 dissection of the gluteal region of the pelvic limb. 



(6) A. ohturatoria. — The obturator artery continues the direction 

 of the pai-ent vessel, sweeping along the iliac portion of the internal 

 obturator muscle to the obturator foramen. It passes through the 

 foramen by insinuating itself underneath the pubic portion of the 

 internal obturator muscle, and thus gains the deeper part of the 

 medial aspect of the thigh, where it is encountered during the dissec- 

 tion of the pelvic limb. 



Just before the obturator artery reaches the psoas tubercle it 

 gives off a large branch, the lateral circumflex artery of the thigh 

 (a. circumflexa femoris lateralis), which passes between the ilium 

 and the ilio-psoas muscle to ramify in the superficial and middle 

 gluteal, tensor fasciae latae, lateral vastus and rectus femoris muscles. 

 The circumflex also furnishes the nutrient artery of the ilium (a. 

 nutritia ossis ilium). 



V. HYPOGASTRICA. — The hypogastric vein is formed by the union 

 of tributaries corresponding to the branches of the arter}^ except that, 

 most commonly, the ilio-lumbar and last lumbar veins join the common 



