XIIL] THE FROG. 237 



a. The anterior division (carotid trunk} : it, after 

 giving off a branch (lingual artery) which runs 

 up the throat, ends in a small red body, the 

 carotid gland, from which other arteries pro- 

 ceed. 



/?, The systemic aortic arch: this is the middle 

 and largest division : it runs round the throat 

 towards the vertebral column, giving off on 

 its way the subclavian artery which runs to 

 the fore-limb. 



y. The pulmo-cutaneous artery, or posterior di- 

 vision of the aortic arch : it runs to the root 

 of the lung, giving off on its way a cutaneous 

 branch which runs out to the integument 

 about the shoulder. 



b. Imbed in paraffin an aortic arch which has been 

 hardened in spirit and cut transverse sections 

 of it : examine with i inch obj. Note the two 

 partitions subdividing it into three channels. 



6. The dorsal aorta and its branches. 



a. Remove the kidneys with vena cava inferior and 

 the generative organs : the dorsal aorta is then 

 laid bare lying on the bodies of the vertebrae. 



b. Follow the systemic aorta (5, a, /?) round the 

 neck; they will be found to unite beneath the 

 vertebral column to form the dorsal aorta. 



c. Follow the aorta backwards: it gives off many 

 branches on its course; note the large one (cce- 

 liaco-mesenteric artery} arising from it just below 

 its point of formation. 



