200 HOW BODY CONTROL IS BROUGHT ABOUT 



medulla. This band of fibers is called the pons. The medulla is, 

 in structure, part of the spinal cord, and is made up largely of fibers 

 running longitudinally. 



Olfaciorylobe 



-Olfactory lobe.rrs Olfactory lobe ...,yy Cerebrum 



Cerebrum 



\Opfic 

 lobe 



Cerebellum 

 LMedulla 



\ \ Cerebrum, 



Cerebellui 

 IfM Opficlobe. 



KWiJIedulla \^ 



Cerebellum. 

 Medulla.., 



.Spinal cord L..Splndlcord 



Cerebellum: 



Medulla..^ 

 ...Spinal cord.. 



f^rog Bird Mammal 



Compare the brains of these four animals. 



The Autonomic Nervous System. — Connected with the medulla 

 is that part of the nervous apparatus which controls the muscles 

 of the digestive tract and blood vessels, some of the secretions, and 

 many functions which have to do with life processes in the body. 

 This is called the autonomic nervous system. 



Functions of the Parts of the Central Nervous System of the 

 Frog. — From careful studies of living frogs, birds, and some mam- 

 mals scientists have learned much of what is known of the functions 

 of the parts of the central nervous system in man. 



It has been found that if the entire brain of a frog is destroyed 

 or separated from the spinal cord, the frog will continue to live. 

 It will not move or croak, but if acid is placed upon the skin so as 

 to irritate it, the legs make movements to push away and to clean 

 off the irritating substance. The spinal cord is thus shown to be 

 a center of defensive movements. If the cerebrum is separated 

 from the rest of the nervous system, the frog seems to act a little 

 differently from the normal animal. It jumps when touched, and 

 swims when placed in water. It will croak when stroked, or 

 swallow if food is placed in its mouth. But it manifests neither 



