THE VASCULAR SYSTEM 



131 



blood into the external gills and their branches : from these the 

 blood passes through short wide capillary loops into the efferent 

 branchial vessels, EF t and EF,, which carry it, now aerated, to 



AR 



CA 



CP 



RT 



KA 



FIG. 31. Diagrammatic figure of the head and fore part of the body 

 of a 6J mm. tadpole, showing the arrangement of the branchial vessels 

 as seen from the ventral surface. The heart has been removed, x 33. 



A, dorsal aorta; AF], AFj, AF 3 , afferent branchial vessels of the 

 first, second, and third branchial arches; AP, pulmonary artery; 

 AR, anterior cerebral artery; CA, anterior commissural artery; 

 CP, posterior commissural artery : the arterial circle formed by these 

 commissural vessels with the carotid arteries surrounds the infundi- 

 bulum of the brain : EFi, EFo, EFs, EF.|, efferent branchial vessels of 

 the first, second, third, and fourth branchial arches ; EH, efferent 

 hyoidean vessel ; EM, efferent mandibular vessel ; GE, external gill ; 

 GM, g'lomerulus ; KA, segmental or archinephric duct; KP, head 

 kidney or prontphros ; KSi, KSs, first and third nephrostomes of 

 pronephros ; RT, truncus arteriosus. 



the dorsal aorta in the roof of the pharynx. The dorsal aortne 

 of the two sides run forwards as the carotid arteries, AC, to 

 supply the head and brain, and also run backwards in the roof 

 of the pharynx, the aortse of the two sides meeting and uniting 



