XIII.] THE FROG. 195 



b. It will be seen that the two auricles contract 

 together; immediately after them, the ventricle ; 

 and then, instantly, the bulbus arteriosus. 



c. Raise the ventricle so as to see the venous sinus ; 

 note that it contracts immediately before the 

 auricles. 



6. The parts exposed by the preceding dissections 

 (B. 1. 2). 



D^aw them carefully without disturbing them. 



a. The throat-muscles: through the broad thin mus- 

 cle in front (mylo-hyoid) is seen the hypoglossal 

 nerve. 



b. The larynx : forming a hard prominence in the 

 middle line, just in front of the aortic arches. 



c. The heart and aortic arches (see B. 5. i.) : the 

 three terminal branches of the latter, viz. 



a. The carotid trunk; the anterior division ; end- 

 ing in a small reddish body (the carotid gland). 



/3. The systemic aortic arch. 

 7. The pulmo-cutaneous artery: the hindmost 

 branch. 



d. The liver: a great brown two-lobed mass; its 

 left lobe the larger and subdivided into two. 



e. The lungs : the posterior ends of these may be 

 seen as sacculated pouches, one on each side of the 

 liver, but they are frequently not visible until 

 the latter organ has been removed. 



f. The stomach: a small portion of this is seen 

 projecting beyond the lower left border of the 

 liver. 



132 



