THE VASCULAR SYSTEM 



135 



In tadpoles of 12 mm. length, in which the opercular gills 

 are fully established, and the external gills shrivelling up, the 

 condition of the bloodvessels is shown in Figs. 33 and 34. 



The truncus arteriosus divides at once into right and left 

 branches, which run straight outwards in the floor of the 

 A GM AB AU Efc Efc 



AY flR 



AT 



AS 



Cf\ 



/ 



VO A FA RB 



FIG. 34. A diagrammatic figure of the head and neck of a 12 mm. 

 tadpole from the ri^ht side to show the heart and branchial vessels. 

 The gills and the gill capillaries are not represented, x 35. 



A, dorsal aorta ; AB, basilar artery ; AFi, AFj, AF<, afferent 

 branchial vessels of first, second, and fourth branchial arches ; AL, 

 lingual artery ; AP, pulmonary artery ; AR, anterior cerebral artery; 

 AS, posterior palatine artery; AT, anterior palatine artery; AU, 

 cutaneous artery ; AY, pharyngeal artery ; CA, anterior commissural 

 vessel ; CO, carotid gland ; CP, posteiior commissural vessel ; EFi, 

 EF2, EF.i, EF4, efferent branchial vessels of first, second, third, and 

 fourth branchial arches; GM, glomerulus ; RA, right auricle; RB, 

 left auricle ; RT, truncus arteriosus ; RV, ventricle ; VD, Cuvierian 

 vein ; VH, hepatic vein ; VI, posterior vena cava ; VP, pulmonary vein. 



pharynx. Each of these branches divides, after a short course, 

 into three vessels, and the hindmost vessel again into two. In 

 this way the four afferent branchial vessels, A Fj, A F 2 , A F 8 , A F 4 , 



