CFI. IX.] 



VOLUNTARY TETANUS 



105 



problem in man. The instrument employed is termed a transmis- 

 sion myograph. The next figure shows the recording part of the 

 apparatus. 



It is called a Mare/s Tambour. It consists of a drum, on the 

 membrane of which is a metallic disc fastened near one end of a 

 lever, the far extremity of which carries a writing point. The interior 

 of the drum is connected by an india-rubber tube (seen at the right- 

 hand end of the drawing) to a second tambour called the receiving 



Screw to regulate elevation of lever 



i 



Writing lever. Tambour. Tube to receiving 



tambour. 



FIG. 125. Marey's Tambour, to which the movement of the column of air in the n'rst tambour is 

 conducted by a tube, and from which it is communicated by the lever to a revolving cylinder, so 

 that the tracing of the movement is obtained. 



tambour, in which the writing lever is absent. Now if the receiving 

 tambour is held in the hand, and the thumb presses on the metallic 

 disc on the surface of its membrane, the air within it is set into 

 vibrations of the same rate as those occurring in the thumb muscles ; 

 and these are propagated to the recording tambour and are written 

 in a magnified form by the end of the lever on a recording travelling 

 surface. 



The tracing obtained is that of an incomplete tetanus, which by a 



FIG. 126. Tracing of a voluntary contraction of the opponeus pollicis on a slowly moving drum, by 

 means of the transmission myograph. The vertical lines indicate seconds. (Schiifer, Canney, and 

 Tunstall.) 



time-marker can be seen to be made up of 10 to 12 vibrations a 

 second. A typical tracing is shown in the above figure (fig. 126). 



