26 



ANIMAL BIOLOGY. 



[Part I. 



carries blood to the head (carotid, ca.), and to the tongue 

 (lingual, //.); the mid-branch curves back and passes to the 

 dorsal side of the heart to supply the body with blood (systemic 

 aorta ao. in 7, and sy. ao. in 10); the posterior branch passes 



cl.ao. 



FIG. 9, iv. HEART OF FROG. 

 (i., ii., and iii. may here be disregarded.) 



to the lung (pulmonary, p.], giving off also a (cutaneous) branch 

 (10, cu.) to the skin. The left branch of the two into which the 

 truncus arteriosus splits divides in the same way. The two 

 systemic aortic arches, right and left, curve round and pass to the 

 back of the heart, and after giving off a branch to the fore-limb, 

 ere long meet in the middle line beneath the back-bone, fusing 

 together to form the dorsal aorta (Figs. 8 and 10, d. ao.), 1 which 

 runs backwards in the large subvertebral lymph sinus (Sv. I. s.) shown 

 in Fig. 8. Where the two aortic arches join to form the dorsal 

 aorta (or from the left arch just before it joins its fellow), a 

 large branch (coeliaco-mesenteric, 10, c. m.) passes off to supply the 

 stomach and intestines with blood. Other branches are given 

 off further back to the kidneys (ren., Fig. 8). While posteriorly 

 the aorta bifurcates to supply the two legs (Fig. 11). 



All these blood-vessels which^ supply the organs with blood 

 1 See note, p. 28. 



