214 



Mr. G. J. Romanes on the 



[May 3, 



rise from 80,000 to 600,000 Ohms, and the anodic break from 15,000 to 

 400,000 Ohms. 



§ 2. The rapidity with which this abnormal excitability declines after 

 the injury is, as already stated, considerable. The following instances, 1 

 which refer to the anodic break, will serve to show this : — 



Time. Degree of Excitability in Ohms. 



Before cutting 13,000 



2 seconds after cutting 280,000 



30 „ „ 244,000 



1 minute „ 210,000 



2 minutes „ 170,000 



3 „ „ 150,000 



4 „ „ 134,000 



5 „ „ 100,000 



Another instance : — 



Before cutting 22,000 



2 seconds after cutting 300,000 



30 „ „ 230,000 



1 minute „ 180,000 



2 minutes „ 150,000 



3 „ „ 130,000 



4 „ „ 110,000 



5 „ „ 95,000 



6 „ „ 80,000 



7 „ „ 73,000 



8 „ „ 67,000 



9 „ „ 60,000 



10 „ „ 54,000 



15 „ „ 25,000 



20 „ „ 13,000 



I may here state that if the excised gastrocnemius be inserted under 

 the skin of a freshly kil]ed frog, and the latter be kept in a moist cool 

 place, the nerve will sometimes retain its irritability for 48 hours or 

 more — the muscle, when placed on the electrodes at the end of that time, 

 still continuing to respond to the kathodic make and to the anodic break. 

 But of course a very much stronger current is now required to produce 

 these responses than was required to do so when the nerve and muscle 

 were in a fresh state. 



§ 3. A strong voltaic current, or a strong induction-shock, allowed to 

 break into an uninjured nerve-trunk, causes in the latter an increase of 

 excitability analogous to that which is caused by mechanical injury. Thus, 

 for example, a momentary exposure of an uninjured sciatic to the full 



