THE VASCULAR SYSTEM. 



137 



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 



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

 a 6| 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 : AFi, AF2, AF3, afferent branchial vessels of the first, 

 second, and third brancliial arches : AP, pulmonary artery : AR, anterior 

 cerebral artery : CA, anterior commissural artery : CP, posterior com- 

 missural artery : the arterial circle formed by these commissural vessels 

 with the carotid arteries surrounds the infundibulum of the brain : 

 EFi, EF2, EF3, EF4, efferent branchial vessels of the first, second, third, 

 and fourth branchial arches : EH, efferent hyoidean vessel : EM, efferent 

 mandibular vessel : GE, external gill : GM, glomerulus : KA, segmental or 

 archinephric duct : KP, head kidney or pronephros : KSl, KS3, first and 

 third nephrostomes of pronephros : RT, tr uncus arteriosus. 



about the junction of head and body to form the single 

 systemic aorta which supplies arterial blood to all parts of the 

 body. 



Besides the complete sets of afferent and efferent branchial 



