68 ZOOTOMY. 



159. The femoral veins (Fig. 17, fin) bringing the blood from 

 pelvic fins : each divides into two trunks : one, the ilio-haemorrhoidal 

 vein {il.h), passes at first backwards and inwards, then forwards 

 along the lateral surface of the rectum and cloaca, and opening finally 

 into a posterior prolongation of the cardinal sinus : the second of the 

 two veins into which the femoral divides is the epigastric vein 

 i'Pg) ; it passes almost directly forward along the lateral wall of the 

 abdominal cavity, receiving veins from the abdominal walls iflb), and 

 finally unites with the brachial vein {br). 



It will be seen from Fig. 17, that the brachial, epigastric and ilio- 

 hsemorrhoidal veins really form one continuous trunk, opening anteriorly 

 into the precaval, posteriorly into the cardinal sinus, and receiving veins 

 from the pectoral and pelvic fins, the abdominal \\'alls, and the rectum 

 and cloaca. The anterior portion of the epigastric should probably be 

 considered as representing the mammary vein of mammals, the two 

 being continuous instead of merely anastomosing. 



160. The common carotid artery (Fig. 20, c.c), a small vessel 

 springing from the efferent branchial vessel of the hyoid arch : it first 

 passes somewhat inwards, and then directly foruards near the outer 

 edge of the base of the skull, sending a branch inwards — the internal 

 carotid artery {i.c) — which unites with its fellow of the opposite side 

 to form an azygos trunk which perforates the base of the skull and is 

 distributed to the brain, especially to the pituitary body and saccus 

 vasculosus (§§ 176 and 177) : the external carotid {e.c) then passes 

 forwards and slightly outwards, and sends branches to the jaws, 

 snout, &c. 



161. The vertebral artery (Fig. 20, vr), a small trunk arising from 

 the first of the three efferent branchial trunks : it passes inwards and 

 slightly forwards, perforates the base of the anterior vertebral plate 

 (§ 3), and is distributed to the brain and spinal cord, on the ventral 

 surface of which it forms, with its fellow, a plexus. 



162. A small hyoidean artery (Fig. 20, hy) given off from the 

 first efferent branchial : it passes to the dorsal side of the hyomandi- 

 bular and sends a branch to the pseudobranchia. 



XXXIX. Remove tvsfo of the gills and make out, in 

 one by dissection, in the other by transverse 

 sections 



163. -The cartilaginous branchial arch which supports 

 the inner edge of the gill. 



