THE SNAKE. 99 



DISSECTION OF THE SNAKE. 



For dissection get a large specimen ; a live one is better, 

 as after severing the spinal cord at the neck (which is 

 essentially the same as cutting off the head), the beating 

 of the heart may be seen, and the persistent vitality of the 

 nerves and muscles serve well to illustrate reflex action of 

 the spinal cord. Lay the snake's head on a board, and 

 with a knife cut entirely through the spinal column, just 

 back of the head; but do not cut off the head. This 

 destroys its sensibility. Get a paper of tacks, and a board 

 as long as the snake. Lay the snake on its back, with the 

 head at one end of the board. Push the point of a tack 

 into the mouth at one side, and drive it through the upper 

 jaw, leaving the lower jaw free. Repeat with the other 

 side. Stretch the snake out straight, and tack through 

 the tail, just back of the vent. With the forceps pinch 

 up a fold of the skin of the throat, and cut through it 

 with the scissors ; continue the cut back along the middle 

 line of the belly, being very careful not to cut anything 

 within. As the cut proceeds, stretch the skin out at the 

 sides, and tack it down every two or three inches. Cut 

 away the thin membrane which extends across from the 

 ribs on each side, avoiding blood-vessels. 



1. With forceps seize the lower jaw and pull the mouth 

 open. Note how dilatable the mouth is, and how 

 loosely the lower jaw is hinged to the upper; note, 

 also, that the right and left halves of the jaws do not 

 unite in front. Examine closely the teeth, their 

 shape and arrangement. 



