STUDIES OF THE NERVOUS SYSTEM 



211 



the secretions of various glands, 

 are largely under the control of 

 the autonomic system. Emotions 

 affect the autonomic system, and 

 consequently circulatory and glan- 

 dular disturbances follow or ac- 

 company emotions. If a plexus is 

 injured, a violent reaction in cer- 

 tain internal organs would natu- 

 rally follow. 



Studies of the nervous system. 



o'x'xi i. ui i_ The ganglia of the autonomic nervous 



Scientists have been able tO Show system are connected with the central 



that there are many similarities in nervous system by nerve fibers, 

 the nervous systems of man and other vertebrates. Probably 

 one of the outstanding differences is the fact that man's cere- 

 brum is generally larger and heavier, proportionately, than that 

 part of the brain of any lower animal. The lower down the 



associative 



spinal 

 cora 



^ spinal 

 -'' nerves 



ctiain. of 

 gctnglioc 

 of autonomic 



imcscle. 



There are three types of neurons. Some take sensory stimulations into the body, others 

 take motor or glandular stimulations out to muscles or glands to bring about a response. A 

 third type, known as the associative neuron, may lie between the other two types of neurons and 

 set up connections between them. 



