THE NERVOUS SYSTEM 117 



EXERCISE 106 

 THE NERVOUS SYSTEM 



Apparatus and Materials. Model of brain (?), brain of calf or sheep, 

 piece of spinal cord, pair of dividers. 



a. Read 399, 400, and 401, of the text. If your school has 

 a model of the human brain, study it, and identify its parts. 



Ask your butcher to get for you the brain of a calf or sheep, 

 and study its form and appearance. Have him also get a piece 

 of the spinal cord; describe a cross-sectional view of it. 



A section of the spinal cord may be found in the proper cuts 

 of sirloin of beef. Ask the butcher to show you one. 



6. With your finger feel for the nerve at the elbow ("crazy 

 bone"); what sensation is produced? When you hit the crazy 

 bone against a hard object, where do you feel the tingling 

 sensation? Why? 



c. Cross your middle finger- over your first finger, and hold a 

 pencil between the crossed ends of the fingers. How many 

 pencils do there seem to be? Why? 



d. Close your eyes, and have some'one touch the skin of your 

 neck, hands, finger tips, forehead, and forearm, with a pair of 

 " dividers." The two points of the dividers should be varying 

 distances apart; sometimes one point should be used, sometimes 

 both points. Where do you find the skin very sensitive; that 

 is, where can the two points be distinguished as two, even when 

 they are only a very small distance apart? 



EXERCISE 107 

 THE EYES 



Apparatus and Materials. White paper, light-pink paper, printed 

 letters % of an inch high, circle of red paper, model of the eye (?). 



a. Read 414 to 418, inclusive, of the text. On a piece of 

 paper make two circles (entirely black) about % of an inc h in 



