210 VERTEBRATES. 



2. The dilatability of the mouth and throat. 



3. The position, shape, and direction of the teeth. Are 

 they adapted for chewing food ? In what condition does 

 the snake swallow its prey ? 



With forceps draw the forked tongue from its sheath, 

 and note its character and length. 



Find behind the tongue a small opening into the trachea, 

 the glottis, and behind the glottis the opening into the 

 esophagus. 



With sharp scissors split the abdominal wall down the 

 median ventral line to the tail. Fasten the cut edges 

 wide apart with tacks. 



Internal Features. Without further dissection make 

 out the following parts: 



1. The heart lies in the central anterior portion of the 

 body, inclosed within its thin transparent pericardial sac. 

 The large conic posterior portion is the ventricle. The 

 two lobes beside its anterior end are the auricles. 



2. The brownish elongated organ lying along the left 

 side of the body is the liver. 



3. Beneath the liver is the stomach. Leading from the 

 mouth to the stomach is the esophagus, and posterior to 

 the stomach is the intestine. 



4. Posterior to the liver, and lying close to the begin- 

 ning of the intestine, is the dark gall bladder. Close be- 

 side it is the spherical spleen. 



F. Posterior to these are the elongated, light-colored 

 kidneys, one on either side, communicating with the 

 exterior by a very long and much crimped duct. 



6. Posterior to all these are the paired reproductive 

 organs, each with a separate straight duct lying alongside 

 that of the kidney. 



Lungs and Blood Vessels. From the glottis the ringed 

 trachea may be traced back to the pink lung, which lies on 



