176 ANIMAL PHYSIOLOGY. 
mary coil, secondary coil, magnetic interrupter, and a scale 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. 
‘ee 
Fie. 172. 
Fie. 172.—Pfliiger’s myograph. The muscle may be fixed to the vise C in the moist-chamber, 
the vise connecting with the lever £ E, the point of which touches the plate of smoked 
glass G. 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 Rosenthal). 
Fie. 173.—Tetanizing key of Du Bois-Reymond (after Rosenthal). Wires may be attached at b 
andc. When d is down the current is ‘‘ short-circuited,” i. e., does not pass through the 
wires, but direct from c through d to b, 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. 
Fie. 173. 
. 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. 173. 
The moist chamber, or some other means of preventing the 
drying of the preparation, which would soon result in impaired 
action, followed by death, is essential. A moist chamber con- 
sists essentially of an inclosed cavity, in which is placed some 
wet blotting-paper, etc., and is usually made with glass sides. 
The air in such a chamber must remain saturated with moist- 
ure. 
