200 VERTEBRATES. 



Kill the animal with chloroform. The best way to do 

 this speedily is to draw the head forcibly out with a 

 tenaculum, open the mouth, find the opening into the 

 trachea at the base of the tongue, and with a syringe or 

 a large pipette inject into it, and through it into the 

 lungs, a teaspoonful more or less of chloroform. 



When the muscles are relaxed, draw out the head, 

 noting the length of the neck and the position it assumes 

 when retracted. Note the horizontal extension of the 

 legs, their length, and range of movability. Find three 

 principal divisions in each, as in the frog. Notice in the 

 sides of the body the " pockets " into which the retracted 

 legs fit. 



Examine the head. Note its shape. Note the relative 

 size and position of nostrils, eyes, and ears. Note the 

 position of the nictitating membrane of the eye ; the color 

 of the iris. 



Open the mouth and examine the beak, which consists 

 of the horny sheaths which incase the edges of the jaws. 

 Observe how these sheaths fit together when closed. Find 

 two nostril openings into the roof of the mouth ; openings 

 of two Eustachian tubes on the sides, back of the muscles 

 which close the jaws (not easily seen from the front, better 

 seen when the head is dissected) ; the opening into the 

 trachea, on the floor of the mouth, and the esophagal 

 opening behind it. 



Observe that the horny sheaths of the jaws, and also 

 the scales forming the external layer of the shell, are con- 

 tinuous with the skin of the body. Both are thickened 

 outgrowths from its outer (epidermal) layer, similar in kind 

 to the smaller scales found on certain parts of the skin. 



Dissection. With a saw or chisel cut through the 

 bony bridges between carapace and plastron. Place the 

 turtle on its back. Cut the plastron free from the skin 



