AMPHIBIA 211 



cord. On each side also a large branch arises, the subclavian 

 or brachial artery, for the supply of the fore-limb. Just after 

 the fusion of the two vessels of the arch the dorsal aorta 

 passes into the median coeliaco-mesenteric artery, which 

 descends in the mesentery to the stomach, liver, pancreas, 

 spleen, and intestine. The dorsal aorta then passes between 

 the two kidneys, liberating renal branches, gonadial arteries 

 and lumbar arteries, the last to the muscles of the body wall. 

 It terminates by dividing into the two iliac arteries which 

 supply the hinder limbs. The iliac gives off a hypogastric 



Carotid 



Aorta- 

 Pulmo-cutaneous <C~^^WMbs=^ ^Pulmon. v. 



'Sinu-aur. opening 



Long, valve 



.\&JitltJllIM'jf,fHIU]lf 3 IE?-^TV 



-Aur.-vent. valve 



FIG. 107. Diagram of heart. After Howes. 



branch to the bladder and body wall, and afterwards divides 

 into femoral and sciatic arteries. 



The carotid divides into lingual and carotid branches. 

 At the base of the latter is the pigmented, spongy, plexiform 

 swelling of the vessel, the carotid gland, which interrupts 

 to some extent the flow of blood past the point, and is 

 probably endocrinal in function as well. 



The action of the heart is a wave-like succession of pulsa- 

 tions beginning in the sinus venosus and ending in the conus. 

 The valves in succession prevent the return of the blood, 

 and thus each chamber is emptied in turn and is ready for a 

 further supply. After the pulsation of the conus the chamber 

 is empty, and the blood is held by the semilunar valves at the 



