XX 



c. 



MUSCULAR AND ALLIED SYSTEMS. 



Protoplasm of plants and animals is contractile, the contrac- 

 tion possibly being chiefly or alone seated in its spongioplasm. 

 In animals alone is a definite muscular system developed. 

 Contraction dependent on life. 



D. 



NERVOUS SYSTEM. 



Consists essentially of cells and fibres. The cells emit and 

 receive nervous impulses ; the fibres conduct them. The cells 

 may be permanently modified by impulses received (memory, 

 instinct). 



Functions. The stimulation and regulation of the contractions 



o 



of the muscular system. By its sensory or afferent nerves 

 making the movements of the body appropriate to its surround- 

 ings. Possibly directly influencing nutrition (trophic nerves). 



Plants. 



The continuity of the protoplasm in Plants allows the stimu- 

 lation at one part to spread and influence neighbouring cells ; 

 the extent of such spreading being in proportion to the inten- 

 sity of the stimulation. They have no nervous system. 



Animals. 



(In all forms below the Vertebrata the entire nervous system 

 may be shown ; but in the Vertebrata their usually large size 

 makes a separation into certain groups convenient, as Brain, 

 Spinal cord, Nerves, Sympathetic or Visceral System.) 



