BABBIT. 131 



and cut off the head. Open the skull to expose 

 the cerebrum and most of the cerebellum. Put 

 the head into formic aldehyde solution (1 to 2 

 per cent.). 



Finish skinning the body (leaving the skin intact 

 in the region of the anus and the scrotal sacs). 



III. The Thoracic Cavity. 



Open the thorax without injuring the diaphragm by 

 a slit on each side of the sternum. Remove the 

 sternum. 



1. Examine the structure of the diaphragm 



(muscle, tendon). 



2. Insert a blowpipe into the trachea and blow 



up the lungs. 



IV. The Circulatory System. 



Open and cut away the pericardium. Dissect off 

 the fat and the connective tissue around the heart 

 and the vessels near to it. 



In young animals the fat-like thymus gland is 

 very conspicuous in the anterior end of the 

 thorax, and sometimes it lies over the anterior 

 end of the heart. 

 Find the parts of the heart : 

 The right and left auricles. 

 The right and left ventricles. (If no division- 

 line can be seen, try to distinguish the two 

 ventricles by feeling the thickness of their 

 walls.) 



