8o THE FROG chap, vi 



nected with the right side of the auricular division. This is 

 the sinus venosus. 



The Arteries. — The two branches of the conus arteriosus 

 just referred to soon branch again. Each divides into three 

 vessels, often spoken of as arterial arches, called respectively 

 the carotid trunk (Fig. 20, car. tr.) the systemic trunk (syst. tr) 

 and the pulmo-cutaneous trunk {put. cu. tr). All these con- 

 form to the definition of an artery given on p. 27, i.e., 

 they are stout, elastic vessels, containing little blood after 

 death, and not collapsing when empty. 



The carotid trunk divides immediately into two, a lingual 

 artery {l.g), which can be traced to the tongue, and a 

 carotid artery {car), which branches repeatedly, its ultimate 

 ramifications going to various parts of the head. At the 

 origin of the carotid is a little rounded mass with a sponge- 

 like interior, the carotid plexus {car. gt). 



The systemic or aortic trunk extends outwards, in contact 

 with the gullet, then sweeps upwards, backwards, and inwards 

 — i.e., towards the middle line — and finally joins with its 

 fellow of the opposite side to form a single median vessel, 

 the dorsal aorta (Figs. 4, 5, and 20, d. ao), which passes 

 backwards, just beneath the vertebral column and between 

 the kidneys. 



As it sweeps round the gullet, the systemic trunk gives off 

 a vertebral artery (Fig. 20, vert) to the vertebral column and 

 part of the head, a subclavian artery to the fore-limb, and 

 an (Esophageal artery to the gullet. 



From the point of union of the two aortic trunks springs 

 a single splanchnic or ccBliaco-mesenteric artery {cml. mes) ; it 

 divides into several branches, which are traceable to the 

 liver {hp) stomach {gs), duodenum {du), spleen {spl) and 

 ileum {int). 



The dorsal aorta gives off on each side four renal arteries 



