A REPRESENTATIVE VERTEBRATE. FROG 



353 



Nucleolus-j 

 Nucleus—] 



Dendrite 

 Neurilemma 



Axon 



;r i V\'f'M i ' i ' ii'i| i. i.ii.ii ^^ 'i'i » i .' i 'a7l i< : i i' i M'ir '| i'ii m.X) 



Cell body 



Dotted lines indicate great length 

 Myelin Node of Ranvier 



■'-««|OUJL '".III 1^1,11 I' PlI'MilL"". ,".1 III 



■—Neurilemma 

 Terminal branches of axon" 



Figure 236. A motor neuron from the spinal cord of man. 



beating of the heart. The autonomic nerv- 

 ous system is composed of two main subdi- 

 visions, termed ( 1 ) parasympathetic ( crani- 

 osacral) and (2) sympathetic (thoracolum- 

 bar), but the details of these divisions are 

 beyond the scope of this book. 



It will be sufficient in this place to point 

 out certain selected points concerning the 

 nervous system of the frog, since general ac- 

 counts of nervous tissue, nervous activity, 

 and the nervous system of vertebrates are 

 presented elsewhere. 



THE NUMBER, NAME, ORIGIN, DISTRIBUTION, AND FUNCTION OF THE CRANIAL 



NERVES OF VERTEBRATES 



According to Hcrrick. it originates from both telencephalon and diencephalon in most species. 



