NERVE TERMINALS. 511 



That only making shocks cause contraction with very weak 

 currents, simply depends on the greater efficacy of the entrance 

 of catelectrotonus into the nerve, which causes the making stim- 

 ulation. 



That contraction follows in all four cases, with medium stimu- 

 lation," is explained by assuming that the depression of the func- 

 tional activity of the nerve is not sufficient to affect its conduct- 

 ivity. 



The want of -response to a making shock, in the case of the 

 strong descending current, depends upon the fact that the part of 

 the nerve near the muscle, around the anode, is in a state of 

 lowered activity, and is, therefore, unable to conduct the impulse 

 which has to pass through this region from the cathode, where 

 the stimulation takes place, in order to reach the muscle. 



The absence of contraction at the breaking of a strong descend- 

 ing current, is caused by the same lowering of the conductivity of 

 the nerve between the point of stimulation and the muscle, because 

 at the cessation of strong catelectrotonus, the region near the 

 cathode rebounds from exalted to depressed activity, and at the 

 moment of stimulation the greater part of the intrapolar region is 

 an electrotonic. 



The specific use of nerve fibres in the body of the higher animals 

 may be thus briefly stated. They form a means of extremely 

 rapid intercommunication between distant parts. The protoplasm 

 of the axis cylinder has undergone a special modification, by which 

 it is enabled to conduct impulses much more quickly than ordi- 

 nary protoplasm does. Even the most nearly-related substance, 

 muscle tissue, transmits impulses about thirty times more slowly 

 than a nerve fibre. A highly organized animal body, without 

 nerve fibres, would be in a worse condition than a highly organ- 

 ized state without a telegraph or even a postal system. 



NERVE CORPUSCLES OR TERMINALS. 



These are the real actors in the nervous operations, while the 

 fibres are merely their means of communicating with one another. 

 One great set of terminals is placed on the surface of the body, 



