TRANSMISSION OF THE EXCITEMENT. Ill 



the constricted nerves, that even if the nerve-sheath is 

 in no way injured, the crushing of the contents of the 

 nerve is in itself sufficient to prevent propagation of 

 the activity. It can be shown that this latter view 

 of the nature of the case is actually correct. For it is 

 possible to determine the time which elapses between 

 the irritation of the nerve and the commencement 

 of muscular pulsation. For this purpose the same 

 methods are applicable as we employed in the case 

 of muscles. Electric measurement of time, or the 

 myograph represented in fig. 17, may be used for this 

 purpose. As however in the present case the point to 

 be determined is, not the form of the muscle-curve, 

 but the moment of its commencement, duBois-Keymond 

 simplified the apparatus so that the curve is drawn on 

 a flat plate, which is pushed forward by spring power. 

 Fig. 28 represents the apparatus. It stands on a strong 

 cast-iron stand from which rise the two massive brass 

 standards A and B. A light brass frame carries the 

 indicating plate, which is of polished looking-glass, 

 1 60 mm. in length by 50 mm. in breadth. The frame runs 

 with the least possible amount of friction on two parallel 

 steel wires stretched between the standards. The dis- 

 tance between the standards is equal to twice the length 

 of the frame, so that the whole length of the plate passes 

 across the indicating pencil when the frame is pushed 

 from standard to standard. Bound steel rods are fastened 

 to the short sides of the frame ; and these rods in length 

 somewhat exceed the path along which the frame passes, 

 and they then pass, with as little friction as possible, 

 through holes in the standards A and B. The end b of 

 one of these rods is surrounded by a steel spring. By 

 compressing this between the standard B and a knob on 



