THE STUDY OP MUSCLE PHYSIOLOGY. 



181 



to determine the relative strength of the current employed. 

 The instrument is put into action by one or more of the various 

 well-known galvanic cells, of which Daniell's are suitable for 

 most experiments. 



Srf^^^^l 



Fig. 169. 



Fig. 168. 



Fig. 168.— Pflliger'8 myograph. The muscle may be fixed to the vise C in the moist 

 chamber, the vise connecting with the lever E E, the point of which touches the 

 plate of smoked glass O. The lever is held in equipoise by H. When weights are 

 placed in scale-pan F, the lever writes the degree of extension effected (after Ro- 

 senthal). 



Fiu. 169.— T'etanizing key of Du Bois-Reymond (after Rosenthal). Wires may be 

 attached at b ana c. When d is down the current is " short-circuited," i. e., does 

 not pass through the wires, but direct from c through d to 6. or the reverse, since 

 b, c, d are of metal, and, on account of their greater cross-section, conduct so 

 much more readily than the wires, a is an insulating plate of ebonite. This form 

 of key is adapted for attachment to a table, etc. 



The access to, or exclusion of the current from, the induc- 

 torium is effected by some of the forms of keys, a specimen of 

 which is illustrated in Fig. 169, 



The moist chamber, or some other means of preventing the 

 drying of the preparation, which would soon result in impaired 



