16 



CHANGES OF EXCITABILITY IN NERVES 



5. The change in site of the indifference-point with increasing 

 strength of an ascending current. 



6. The changes of excitability at the negative pole of a descending 

 current extrapolar. 



7. The changes of excitability at the positive pole of a descending 

 current extrapolar. 



8. The changes of excitability at the negative pole of a descend- 

 ing current intrapolar. 



9. The changes of excitability at the positive pole of a descending 

 current intrapolar. 



10. The change in site of the indifference-point with increasing 

 strength of a descending current. 



The experimental arrangements were as follows (see Fig. i). 



Fig. i. 



From the battery (R 2 ) the current passes to the electro-magnet 

 (E), which elevates the lever of my new mechanical stimulation- 

 apparatus, which I employed in these experiments * (see Kg. a). 

 This current then passes to a Pohl's reverser without the cross wires. 

 If the arms of the reverser dip into the mercury cups i, the current 

 passes directly to the electro-magnet, and the lever is held sus- 



1 Cf. Tigerstedt, 'En ny metod for mekanisk retning af nerver' Nordiskt, Medi- 

 cinal Arkiv, xiii, 1881, Nr. 12. A description of this method will shortly appear in 

 the Zeitschrift fur Instrumentenkunde. 



