THE NERVOUS SYSTEM. 149 



feet in a second ; it goes out at the rate of about ninety feet 

 in a second ; and it takes a little time for the superintend- 

 ent to receive the message, and give the order. Then it 

 takes time for the muscles to contract. 



If the mosquito is quick, he will escape you. 



REFLEX ACTION. 



5, In the night, the general superintendent's office is 

 closed : the cerebrum is asleep. And yet, if the foot is 

 pricked or tickled, it will be drawn up. A frog's brain 

 may be taken out entirely, without killing him. If then 

 his side is pricked, he will scratch it with his foot. This 

 shows us that the general superintendent in the cerebrum 

 does not do all the regulating of the body. There are 

 district superintendents in the spinal cord, and in the 

 medulla ; and some matters are never sent up to the cen- 

 tral office at all. Digestion and respiration and circula- 

 tion are all regulated by district superintendents. 



6, Such actions are called reflex actions; because the 

 message is sent in, and the order for the act " reflected " 

 back, without any action of the will. 



Winking is ordinarily a reflex act. The eye gets a 

 little dry. The message goes in along the nerve fibers, 

 which end just beneath its surface ; and the order comes 

 out to a muscle which brings the lids together, and spreads 

 moisture over the eye. 



Coughing is a reflex act. Something tickles the throat, 

 or the air-passages below; and we can not help coughing. 

 The muscles of expiration combine to throw out the thing 

 that tickles. 



Sneezing is a reflex act, for the purpose of clearing the 

 air-passages above the throat. All these acts are regulated 

 by centers below the cerebrum. 



