Chap, xvii.] MAREY'S MYOGRAPHION. 179 



frog-plate is supported on a brass upright, springing 

 from a metal base on three wheels. The wheels move 

 on rails. Through the base there passes a thick screw 

 with a very fine thread. The screw is turned by 

 clockwork supplied with a regulator, and works on 

 pivots. By the motion of the screw the frog-plate 

 is slowly carried along the rails from one end to the 

 other. By this means, if the recording cylinder be 

 kept revolving, the lines drawn by the stylet do not 

 clash with one another, but each succeeding one, by 

 the movement of the frog-plate, is drawn in front of 

 the other. Now, if at exactly the same point in 

 each revolution of the cylinder the primary circuit 

 were closed and then opened, two curves, one of 

 the closing and another of the opening contrac- 

 tion, would be obtained side by side, and with every 

 succeeding revolution two other curves would be ob- 

 tained, those of one revolution always in advance of the 

 other. This process might be permitted to go on for 

 a half or one hour, and at the end of that time one 

 would have on the cylinder a register of the variations 

 in the form, height, etc., of the muscle curve due to 

 the constant repetition of the stimulus ; a registration 

 of fatigue would be obtained. On the same cylinder 

 time could be marked by the chronograph, so that one 

 could gauge how fatigue affected the speed of con- 

 traction and relaxation. An apparatus has been 

 adapted to the cylinder for the purpose of stimulating 

 muscles and nerves at certain moments in the revolu- 

 tion of the cylinder, but a very simple arrangement 

 easily accomplishes this in the ordinary cylinder. 

 To the circumference of the end of the cylinder b, 

 or to the axis, a small piece of copper wire can 

 easily be fixed with solder. This projects down wards 

 from the outer end of the cylinder. A shallow, 

 dish containing mercury is then placed beneath the 

 cylinder, or a wooden trough can be adapted in 



