422 MANUAL OF ZOOLOGY sect. 



into carotid (Figs. 252, car. a and 253, car) and lingual (Ig) 

 arteries for the supply of the head, the former having at its 

 base a small swelling, the carotid gland (car. gl), consisting 

 of a plexus of blood-vessels. The systemic trunks curve 

 round the gullet and unite with one another above it to form 

 the dorsal aorta (d. ao), from which, or from one of the 

 systemic trunks themselves, the arteries to all parts of the 

 body, except the head, the lungs, and the skin, are given off. 

 The pulmo-cutaneous trunk divides into two, a pulmonary 

 artery (pul) to the lung, and a cutaneous artery (at) to the 

 skin. 



The blood from the head and fore-limbs is returned by 

 veins which unite to form a pair of large trunks, the pre- 

 cavals, which open separately into the sinus venosus. 



One portion of the blood from the hind-limb is carried 

 forward by a vein which unites with its fellow of the oppo- 

 site side to form the abdominal vein (Fig. 254, abd), which 

 passes forwards, in the ventral body-wall, to the level of 

 the sternum, where it turns inwards and divides into two 

 branches, both breaking up into capillaries in the liver. 

 Just as it enters the liver it is joined by the hepatic portal 

 vein (hp.pt), bringing the blood from the stomach, intes- 

 tine, spleen, and pancreas. The rest of the blood from 

 the hind-limb is carried by the renal portal vein to the 

 corresponding kidney. 



The blood is collected from the kidneys by the renal 

 veins (m), which unite to form the large unpaired post-caval 

 vein (pt. cv). This passes forward through a notch in the 

 liver, receives the hepatic veins (hp) from that organ, and 

 finally opens into the sinus venosus. Thus the blood from 

 the hind-limbs has to pass through one of the two portal 

 systems on its way back to the heart ; part of it goes by the 

 renal portal veins to the kidneys, and thence by the renal 



