THE COMMOX FROG. 



133 



passes backwards as the great dorsal (in man descend- 

 ing) aorta, giving off arteries to all parts of the body. 

 The third, or pulmo-cutaneous trunk (3) ends by 

 dividing into two arteries. The anterior of these (r) 

 goes to the skin (which, as we have seen, is in the 



Fig. 77. — The Frog's Heart. The ventricle is helow s, the aortic bulb is on the left of 

 s, and ends in six aortic trunks, three on each side. The first of these (i) ends 

 in the carotid gland {a), whence spring the lingual (/), and the carotid {c), 

 arteries The second trunk (2) is the root of the great dorsal aorta. The third 

 trunk (3) ends in the pulmo-cutaneous artery' (r), and the pulmonary artery (^), 

 which is shown sending ramifications over each lung. 



frog an important agent in respiration), the posterior 

 one (/) goes to the lungs. 



The heart itself is of a more or less spongy texture, 

 but the main cavity of the single ventricles opens at 

 its extreme right into that of the aortic bulb {c). In 

 close proximity to the opening are the openings from 

 the right {b) and the left {a) auricles respectively. 



