r^- 



F 



36 



THE BE GINNINGS OF LIFE, 



in texture^ and that are shielded in an unusual manner 



"from disturbing forces, except at their 



1 ^ 



two 



extre^ 



mities V On the one hand, these fibres connect peri! 

 pheral parts with the nerve-centres, whereby such parts 

 are rendered sensitive -y whilst, on the other hand, the 

 nerve-centres are also in connection with other sets of 

 nerve-fibres which are accustomed to transmit stimuli 

 outwardly towards the muscles in which they are dis- 

 tributed, so as to call them into activity. The expe- 

 riments of Phillipeaux and Vulpian have abundantly 

 confirmed the reasonings of Mr. G. H. Lewes ^, whidi 

 went to show that there was no real difference in pro- 

 perty between the so-called sensory and motor nerves. 

 The fundamental property of each alike is the capa- 

 bility of transmitting a stimulus, and for this property 



r 



Mr. Lewes proposed the name neurlllty. Neurility, 

 therefore, is the characteristic property of a nerve, just 

 as contractility is the characteristic property of a muscle; 

 and the different results produced, when a sensory and 

 a motor nerve respectively are stimulated, is due to the 



dif]^erent nature of the organs to which the stimuius is 



t 



directed. When the stimulus traverses the nerve in 

 an afferent direction, this, impinging upon a nerve- 

 centre^ liberates a larger or smaller quantity of energy, 

 and may produce what is called a sensation ; but when, 

 on the other hand, a stimulus originating in a nerve-, 

 centre is propagated in an ejferent direction, then this 



1 > 



Principles of Psychology,' 1869, No. 20, p. 24 

 ^ 'Physiology of Common Life,' 1859. 



\ 



\ 



,\\0 



!i]S 



calls 



ives 



n 



in 



a 



we have ^ 

 As ^^ ^t 



, t its co^^'^' 



'' 'of the ani: 



This, after the d 

 transmitting a si 

 .war ( when stin 



to which it is di 



during 



which tk 

 portion as the ai 

 Again, there are 

 kind on record v 

 the nervous syst: 

 Without this al 

 thus cut off fron 

 experiments of 

 the posterior pai 

 li^s been cut c 

 the abdominal 



earance 



c 



supervenes 



5 



ma) 



f^^ niinutes by 



main a 



stores to 



rtery. 



throuah 



this , 



a 



ati 



IS to 



say, 





stimuli 

 '^•^% Of th 



