THE FROG 



The blood from the lungs empties into the left auricle by two small 

 veins, one from each lung> 



Blood vessels pass to every part of the body. We know they are 

 everywhere because one cannot insert the point of the finest needle in 

 any part of the body without piercing them, showing they are so close 

 together that one cannot get in between them. Arteries are always rela- 

 tively thicker-walled and more elastic than veins (Fig. 12). 



car.dr 



subcl 



pulm 



, vert 



Fig. 13. The Arterial System of the Frog. 



/., Carotid artery; //., systemic artery: ///., Pulmocutaneous artery. (The" 

 three together being the aortic arches.) ao.c., dorsal aorta; car, carotid artery; 

 car.dr., carotid gland ; coel mes., coeliaco-mesenteric artery ; cut., cutaneous artery ; 

 d, intestine ; gen., spermatic artery ; h., testis ; if., iliac artery ; Leb., Liver ; ing., 

 lung; ling., lingual artery; n., kidney ; occ., occipital artery; occ.vert., occipito- 

 vertebral artery ; pulm., pulmonary artery ; ren., renal artery ; subcl., subclavian 

 artery; tr., truncus arteriosus ; v., ventricle of heart; vert., vertebral artery. (After 

 Meissner. ) 



The principal divisions of the arterial system (Fig. 13) may be sum- 

 marized as follows : 



I. The common carotid ( ) divides into the 



lingual or external carojid, supplying the tongue and neighboring parts, 

 and the internal carotid which gives off the palatine ( ) 



artery to the roof of the mouth, the cerebral carotid to the brain and the 



