620 



Professor Jagadis Chunder Bose 



[May 10, 



acting as a block. In such a case, when A is struck, the indicator 

 will move to the right ; when B is struck, it will move to the left. 

 Thus we obtain effects which are reversible. 



2. Or we may detect the effect of shock by the variations that 

 it may produce in the intensity of the current. Take the case of 

 n, Fig. 2, where there is a permanent difference of level between the 

 two ends ; one end, say B, being also more securely held, so that a 

 shock produces less disturb- 

 ance of level there than at A. 

 As there is a permanent 

 difference of level between B 

 and A, there will be a cur- 

 rent the normal intensity of 

 which (c) will depend on the 

 resting difference of level 

 between B and A. If the 

 pipe be now struck, A will 

 be relatively more disturbed, 

 and there may then be pro- 

 duced either a decrease 

 (B A 2 ) or an increase (B A 1 ) 

 of original difference of level. 

 In the former case we shall 

 have less current (c 1 ), that is 

 to say, the shock will have 

 the effect of a negative varia- 

 tion of current ; in the latter 

 case there will be a greater 

 flow (C) or a positive varia- 

 tion. 



These models may help 

 us in framing a mental 

 image of that electrical vari- 

 ation which constitutes the 

 response to stimulus of a 

 living tissue. 



Current 

 ■ Cm-re-nZ, 



Of acJxcrL 



If we take a piece 

 Electric of living muscle 

 Response, whose surface is 



uninjured, then 

 any two points (A and B) 



Fig. 3. — Magnetic Lever Recorder. ,M 

 muscle ; A uninjured, B injured ends. HE 1 

 non-polarising electrodes connecting A and 

 B with galvanometer G. Stimulus produces 

 "negative variation " of current of rest. 

 Index connected with galvanometer needle 

 records curve on travelling paper (in prac- 

 tice, moving galvanometer spot of light traces 

 curve on photographic plate). Rising part 

 of curve shows effect of stimulus ; descend- 

 ing part, recovery. 



on such surface being 



in a similar 



will be the 



__ited by the 



indicating galvanometer when two non-polarisable electrodes* con- 



molecular condition, their electrical level or potential v 

 same. They are iso-electric. No current will be exhibi 



■*v % in £ rocls in solution of ZnS0 4 , with two dependent strips of cloth, moistened 

 with NaCl solution passed round the muscle at A and B. 



