114 ELEMENTAEY BIOLOGY. [xi. 



passes, from one end of it to the other, like the 

 peristaltic contraction of the intestine in one 

 of the higher animals. 



/3. The auricles ; one of these will be seen on each 

 side if the ventricle be gently pushed out of the 

 way : each is a somewhat pyramidal sac, con- 

 tinuous with the .ventricle at the apex of the 

 pyramid. 



5. The organs of Boj anus. 



a. Divide the alimentary canal at the posterior part 

 of the pericardiac chamber and turn it and the 

 heart forwards, so as to lay bare the floor of the 

 pericardium. Running along the middle line 

 of this floor will be seen a large blood-sinus, 

 the great vena cava; on each side of this, the 

 floor is formed by the roof of a transparent sac 

 (the non-glandular part of the organ of Bojanus}, 

 through which is seen a dark brown mass (the 

 glandular part of the organ of Bojanus). 



I. At the extreme front end of the pericardiac floor, 

 immediately under the point at which the in- 

 testine enters the cavity, will be found a pair of 

 oval openings ; pass into each a bristle, tipped 

 with a small knob of sealing-wax to prevent it 

 from perforating a passage for itself: the opening 

 will be found to lead into a channel which runs 

 along the glandular part of the organ of Bojanus. 



c. Remove carefully the thin transparent roof of the 

 non-glandular part of the organ of Bojanus, on one 

 side, so as to lay bare the portion of the glandular 



