XXXVITI.] INFLUENCE OF TEMPERATURE, ETC. 215 



When the frog is under the influence of the drug, discharge a 

 reflex act by mechanically stimulating the skin of the leg. The 

 limbs are extended, and remain so for several seconds, due to the 

 prolonged contraction of the extensors overcoming the flexors 

 and thus causing extension of the legs. 



(//.) Arrange the induction machine for single shocks to make 

 and break the primary circuit by the hand by means of a contact- 



FlO. 136. Muscle-Curve from a " Veratrised " Muscle, recorded on a Slow-moving 

 Drum. A. Abscissa ; T. Time in seconds. 



key. Short-circuit the secondary. Do not stimulate the muscle 

 often, as the veratria effect diminishes with activity of the muscle. 



(c.) Make a nerve-muscle preparation and fix it on a crank- 

 myograph. On dividing the spinal cord notice the prolonged 

 extension of the legs. 



Arrange the muscle-lever to record its movements on a slow- 

 revolving drum (1-2 cm. per second). Take a tracing. Note that 

 the muscle contracts quickly enough, but the contraction is very 

 high compared with that of a non-poisoned muscle, while the 



Fro. 137. Veratria Curve (Upper). Normal Muscle-Curve (Lower). Quick-moving drum. 



muscle relaxes very slowly indeed. The relaxation phase may 

 last several seconds, is., a kind of "contracture." Record half- 

 seconds or seconds under the tracing. The tracing may show an 

 uneven curve, due to irregular spasms of the muscular fibres, or an 

 initial contraction as in fig. 136. 



(d.) Take a tracing with a quick-moving drum, and such a curve 



