12 EXPERIMENTAL PHYSIOLOGY. 



to the primary coil stimulate the tongue by making and break- 

 ing the primary circuit. Move the secondary closer and closer 

 to the primary coil and note the effect produced on the tongue. 

 Again move the secondary out into such a position that it just 

 clears the primary coil. Now study the effect of tilting the 

 secondary coil. 



The Graphic Record. By the use of a lever it is possible to 

 magnify muscle contraction. The movement of this lever is re- 

 corded on smoked paper. The kymograph is devised for carrying 

 the smoked paper. 



Glazed paper is wrapped tightly around the drum of the kymo- 

 graph so that the glaze is outward. The gummed end is fastened 

 to the opposite end so that the paper will not slip and the writing 

 point of the lever will not catch on the overlap. The drum is 

 held in the smokiest part of a gas flame while being rotated rapidly 

 on the brass tube which is maintained horizontally by hand. In 

 this way a uniform coating of carbon can be obtained on the 

 paper. A light chocolate colour is to be preferred to a deep black 

 because there is less danger of burning the paper. 



A small triangular piece of photographic film or waxed paper is 

 fastened by a bit of wax to the end of the lever in order to serve 

 as a writing point. The lever is always on the right hand side of 

 the drum so that when the latter is rotated it pulls away from the 

 writing point. The lever must be at a tangent to the curved surface 

 of the cylinder in order to prevent the writing point leaving the 

 smoked surface when it rises. The writing point may be bent 

 inward to keep the rest of the lever free of the drum. 



When ready to remove the paper from the drum, it is cut at 

 the overlap by a sharp knife in such a way that the knife strikes 

 the under paper and not the drum. A corner of the paper is 

 grasped against the edge of the drum with the other hand so that 

 it will not fall. At this stage the record may be placed on the table 

 and lettering or other explanatory matter inscribed. It is well 

 to place your name and date on each record. The record, with 

 smoked side up, is passed once through a rosin-alcohol solution 

 (120 gm. rosin to 1,000 c.c. of 95% ethyl alcohol) and then hung 

 over the tray to drain. When dry the parts desired are to be care- 

 fully cut out and preserved in the note book. 



