REFLEX MOTIONS. 275 



tion of the sensory nerves of the eye, sneezing on 

 irritation of the mucous membrane of the nose, cough- 

 ing on the irritation of the mucous membrane of the 

 respiratory organ. Wherever sensory nerves are con- 

 nected by nerve-cells with motor nerves, these reflex 

 actions may occur. If an animal is decapitated and 

 its toe is pinched, the leg is drawn up and contractions 

 occur in it. The reflex actions are here accomplished 

 through the nerve-cells of the spinal marrow, and the 

 removal of the brain favours the action, while it at the 

 same time excludes the possibility of the intervention 

 of voluntary movements. 



There is no doubt that in this process the nerve- 

 cells play a part, and that the process does not depend 

 solely on the direct transference of the excitement from 

 a sensory nerve-fibre to an adjacent motor nerve-fibre. 

 Apart from the fact that the transference never takes 

 place except where nerve-cells can be shown to be pre- 

 sent, this is confirmed by the fact that the process of 

 reflex transference occupies a very noticeable time, 

 much longer than that required for transmission 

 through the nerve-fibres. With the knowledge which 

 we have now gained of the structure of the central 

 nervous organs, it may be considered established, that 

 nowhere is there immediate connection between sen- 

 sory and motor nerve-fibres, but a mediate connection 

 through the nerve-cells. This allows the possibility of 

 the propagation of an excitement from a sensory nerve- 

 fibre, through a nerve-cell, to a motor nerve-fibre. It 

 is thus intelligible how, owing to the interconnec- 

 tion of the nerve-cells, the passage of the excitement 

 from any sensory nerve-fibre to any or every motor 

 nerve-fibre is possible, for the excitement advances 



