ADVANCED EXPERIMENTAL PHYSIOLOGY 173 



contraction of the muscles of the trunk 

 and limbs from disturbing the lever 

 connected with the gastrocnemius 

 muscle. 



Strychnine is sparingly soluble in 

 water, 1 in 6,700, but a dose of 10-15 

 minims (0-592-0-888 c.c.) of a saturated 

 solution of the drug in normal tap- 

 water saline solution will in a frog 



produce the characteristic convulsions ^^B^^H^H 'I 

 and death. Such a dose is injected 

 under the skin of the frog's back. 

 Twitches and convulsions soon begin 

 and the contractions of the gastroc- 

 nemius muscle are recorded simultane- 

 ously with the movements of a signal 

 marking seconds (Fig. 162). The num- 

 ber of contractions is about 8 or 10 per 

 second. The stage of incomplete tetanus 

 is followed by prolonged twitches or 

 clonus. If the spinal cord be destroyed 

 by a probe during the stage of tetanus 

 the contractions will cease at once, 

 showing that the convulsions were due 

 to the action of the drug upon the II 



nerve-cells and dendrites in the spinal 

 end. 



Record of a Voluntary Contraction. 

 If a finger be placed upon a muscle 

 voluntarily thrown into contraction, a 

 series of vibrations can be felt. These 

 can be recorded and their rate deter- 

 mined in the following way. 



A receiving tambour, with a button 

 or a piece of cork fixed upon the rubber 

 membrane, is connected with a bellows 

 recorder (Fig. 164) which is arranged 

 to write upon a revolving drum. A 

 chronograph is set up for marking the 

 time in seconds. The button of the 

 tambour is placed upon the adductor 

 pollicis, or the masseter muscle of the 

 subject. When the muscle is volun- 

 tarily contracted the lever shows a 

 number of vibrations ; these are re- 

 corded (Fig. 163). The curve obtained 



resembles an incomplete tetanus with 6 or 8 vibrations per second ; 

 the true rate, as shown by a string galvanometer connected with 

 the muscles, appears to be about 50 per second. 



