110 LABORATORY GUIDE IN PHYSIOLOGY. 



ether upon the cotton in the cone; place the cone over 

 the rabbit's nose; observe, and note carefully every step 

 in the anaesthesia. 



(2) Carefully note the rate of the heart before begin- 

 ning anaesthesia. 



(3) Keep the cotton moist with ether; watch the 

 respiration and pulse, and be careful not to give the 

 animal too much and interrupt the experiment. 



Group " ." Wash the clipped surface of the throat. 



After the rabbit is completely anesthetized, make 

 with scissors a median incision through the skin, be- 

 ginning at the apex of the sternum and cutting anteriorly 



FIG. 19. 



for about 5 or 6 cm., divide the subcutaneous connec 

 tive tissue over the middle of the trachea. Carefully 

 separate from the median line on either side laterally 

 the subcutaneous connective tissue with the associated 

 adipose tissue. 



How many pairs of muscles come into view? What 

 two muscles approach the median line to form the apex 

 of a triangle at the anterior end of the sternum ? Ob- 

 serve a pair of thin muscles lying dorsal to the muscles 

 just mentioned and joining in the median line to form a 

 thin muscle sheet covering the trachea on its ventral 

 side ? What muscles are these ? 



Carefully lift up the median edge of the sterno mas- 

 toid muscle and separate with the handle of a scalpel 



