FACTS 185 



Now suppose that, among the neurons into which a part 

 of the influx may pass, one through its cylindraxis is in 

 relation with a muscular element ; the nervous influx will 

 travel this way to the muscular element and determine 

 in it a rupture of colloid equilibrium ; and this will manifest 

 itself according to the nature of the muscular element, 

 that is, by a modification in the state of contraction of the 

 element. 



Thus, by the intermediary of one or more neurons, a 

 relation is set up between a surface impression received 

 by an epithelial cell and a muscular movement which is a 

 part of the functioning of the locomotor apparatus. This 

 phenomenon has received the designation of " reflex " ; 

 it is an element of the individual's irritability, a part of the 

 individual's manner of reacting against external stimuli 

 according to its nature. 



Consequences beyond measure flow from this disposition 

 of things. 



In the higher animals, indeed, it is no exaggeration to 

 say that there is not one* epithelial cell going to make up 

 the outer wall of the animal's body (Fig. 15) which is 

 not in relation with the extremity of the cylindraxis of a 

 neuron. Now it is across these epithelial elements form- 

 ing the body's surface that take place the exchanges between 

 the being's interior medium and the environment physical, 

 colloid, chemical exchanges. 



We see that the organism is well guarded. Nothing 

 can enter in without making itself felt by means of the 

 neurons in elements situated far from the entrance door. 

 It is like some palace whose every opening is fitted with 

 automatic alarms. 



It remains for us to understand how all this mechanism 

 is co-ordinated so that the muscular contraction, glandular 



