ELECTRICAL CHANGES IN TISSUES 



659 



S 



II 



I"? 



Is- 45 



- *" 



2 o 



a 48 



O V 



lJ 



o 

 Is 



.-S 



3 -fcJ r- 



The electromotive force of the shock, owing to the manner of connection of the 

 plates in series, is naturally 

 greater when these plates 

 are arranged along the 

 length of the fish than 

 when across it. That of 

 Malapterurus, according 

 to the most recent deter- 

 minations of Cremer, with 

 the string galvanometer 

 (see Garten's article, 1910, 

 p. 200), amounts to 450 

 volts. 



It is obvious that, in 

 order to obtain an effective 

 potential difference, the 

 whole of the electrical 

 plates must be excited 

 simultaneously. When 

 they are all innervated 

 from a single neurone on 

 each side, as in Malap- 

 terurus (see page 471 

 above), this is easily ex- 

 plained. But in other fish 

 the centres consist of a 

 large number of cells, 

 106,000 in T<*rpedo, accord- 

 ing to Fritsch. Since each 

 single discharge of the 

 organ only lasts about 

 0'005 sec., the adjust- 

 ment of the reflex activity 

 of the neurones must be 

 very accurate in order that 

 each plate shall be in phase 

 with the others, so as to 

 sum up with them. 



The latent period ap- 

 pears to be no less when 

 the organ is stimulated 

 directly than when through 

 the nerve. This fact may 

 mean that the only active 

 part is the nerve end-plate, 

 or that any other part, 

 such as might be developed 

 out of the muscle fibre, is 

 not directly excitable. 

 After section of the nerves, 

 the direct and indirect 

 excitability of the organ 

 vanish together, contrary 

 to the case of muscle. 



That there is some- 

 thing more than nerve 

 fibre responsible for the 



electrical change is shown by the fact that the organ is much more quickly 

 fatigued than nerve fibre itself, although not so quickly as muscle (Garten, 1910, 



