120 APPLIED PHYSIOLOGY 



to send the orders alone, and thus walking becomes a reflex 

 act. So in learning any new motion, after we have done 

 it a few times our spinal cords send the proper order with- 

 out our thinking of it. 



228. Need of the spinal cord. The spinal cord acts 

 without our knowledge. We do not feel the cells of the 

 body grow, and we do not feel the spinal cord send the 

 orders for their growth. It controls all the vital actions 

 of life. It is well we do not have to think about sending 

 the orders for living, for we might forget them and then 

 we should die. As it is, the cord attends to them wholly 

 without our knowledge. We put food into our stomachs 

 and the spinal cord sees that it is made into living cells 

 and that the cells do their work. We cannot change its 

 work by any amount of thought or effort. An animal's 

 spinal cord does its work as well as a man's. In fact, it 

 has the same kind of work to do and is as perfect as man's. 



SUMMARY 



1. Nerves carry messages from the mind to the cells of 



the body, telling them to act and to eat. The cells 

 also send messages to the mind, telling of their needs 

 and of what is touching them. 



2. Nerves begin in the spinal cord. 



3. The spinal cord is itself made of nerve threads, and 



also of cells in which a part of the mind lives. 



4. The nerve cells of the spinal cord send messages over 



the nerves when told by the mind in the brain. 



5. The cells of the spinal cord also send orders in response 



to information brought by the nerves. This is called 

 a reflex action. Orders to grow and to snatch the 

 body from a sudden danger are reflex acts. 



