THE CHANGE IN FORM 345 



temperatures, diminished at high. Above 30 the 

 excitability to electrical stimuli diminishes stead- 

 ily ; it disappears almost entirely before rigor is 

 reached. 



Influence of Veratrine on the Form of the Con- 

 traction. With a capillary pipette inject in the 

 dorsal lymph sac 5 drops of a 1 per cent solution 

 of veratrine sulphate or acetate. After a few 

 minutes, test for symptoms of veratrine poisoning 

 by pinching the foot from time to time. 



Soon the mechanical stimulation will be fol- 

 lowed by prolonged contraction of the extensor 

 muscles and still more prolonged relaxation. 



Make a gastrocnemius muscle preparation. 

 Fasten the muscle to a muscle lever and bring the 

 writing point against a smoked drum. Eecord a 

 single contraction. 



Note the increased height of the phase of 

 shortening, and the prodigious increase in the 

 duration of the phase of relaxation. This con- 

 tracture (page 340) is lessened by repeated stimu- 

 lation, but reappears if the muscle be allowed 

 to rest. Cooling or warming usually causes the 

 veratrine effect to disappear temporarily. 



A quick initial contraction may precede the 

 characteristic veratrine contraction, possibly be- 

 cause the veratrine affects differently the red and 

 the clear fibres. 



