PRACTICAL STUDY. 47 



J. Poisons. 



1. Note the convulsive twitchings of ihe muscles of a de- 

 capitated frog into which, a few moments previously, the dem- 

 onstrator has injected subcutaneously a trace of strychnine. The 

 convulsions become violent when stimuli are applied, and are 

 caused by the unusual activity of the poisoned protoplasmic ner- 

 vous structures. 



2. Add to a fermenting yeast-fluid, which is giving off bubbles 

 plentifully, a quantity of corrosive sublimate (a violent poison). 

 The yeast is killed, as is proven by the stoppage of the fermenta- 

 tion. 



K. Electricity. 



1. If an interrupted current be sent into a muscle removed 

 from a frog's leg, it will change shape or contract. 



2. Compare the living frog's muscle in this respect with mus- 

 cle in rigor calorls or rigor mortis. (G.) (H.) 



