148 GENERAL PROPERTIES OF LIVING TISSUES 



is quite regular. If tetanus fails to appear, paint 

 the cathodal region with one per cent solution of 

 sodic carbonate, thus raising the irritability, and 

 repeat the experiment. The curve secured in 

 this way is likely to be irregular. 



Produce opening tetanus, and while the muscle 

 is contracting close the current again. 



The tetanus will disappear ; the irritability 

 will be reduced in the anodal region, from the 

 polarization of which the tetanus was produced. 



Open the current again. When the tetanus 

 reappears reverse the pole-changer and close the 

 current. 



The tetanus will be increased ; the irritability 

 in the former anodal region will suffer a catelec- 

 trotonic increase. 



2. A beautiful demonstration of polar excitation 

 may be made in this experiment. Connect the 

 electrodes in such a way that the intrapolar cur- 

 rent shall be descending (i.e. towards the muscle). 

 When the opening tetanus appears, cut away 

 the anode by severing the nerve between the 

 electrodes. 



The contraction ceases with the removal of the 

 source of stimulation. 



3. The stimulating effect of the salts of the 

 alkalies has been explained by their attraction 

 for water, the loss of which increases the effect 



