8o 



VETERINARY PHYSIOLOGY 



electro-positive to the rest of the neuron, just as the contracting 

 part of a muscle is electro-positive to the rest (p. 63). 



3. Conduction in Neurons. When a neuron is stimulated 

 at any point, some time elapses before the result of the 

 stimulation is made manifest, and the farther the point 

 stimulated is from the structure acted upon, the longer is 

 this latent period. This of course indicates that the change, 



FIG. 39. M, Muscle attached to crank lever marking on revolving drum. The 

 secondary circuit of an induction coil is connected with a commutator, 

 with the crossed wires removed so that the current may be sent either 

 through the wires going to the nerve at A far from the muscle, or at B, 

 a point at a measured distance nearer the muscle. On the drum, A 

 represents the onset of contraction on stimulating at A, and B the onset 

 on stimulating at B. To secure stimulation in each case with the drum 

 in the same position, the make and break of the primary circuit is caused 

 by the point K touching and quitting the point P. 



whatever it is, does not develop simultaneously throughout 

 the neuron, but, starting from one point, be it at one end or in 

 the middle, travels or is conducted along. The rate of con- 

 duction may be determined by stimulating a nerve going to a 

 muscle at two points at known distances from one another, and 

 measuring the difference of time which elapses between the con- 

 traction resulting from stimulation at each (fig. 39). {Practical 

 Physiology.) 



