ON LIVING MALAPTERURUS. 



399 



I considered whether the less strength of the posterior half might 

 not depend on the distribution of a single nerve-tube in the whole 

 organ, in consequence of which, the wave of innervation would be 

 weakened before reaching the posterior part of the organ. 



However, before such a theory of the phenomenon can be pro- 

 pounded, another question must be solved. Does the posterior half 

 of the organ act with less electromotive force than the anterior, or 

 does the feebleness of its action result simply from its smaller 

 transverse section, and consequently greater resistance ? Not only is 

 the organ somewhat thinner at the tail, but the diameter of the tube 

 formed by it decreases. The organ indeed decreases somewhat in 

 transverse section towards the head also, but much more gradually. 

 It seemed possible to decide by experiment the question, whether 

 this is the reason of the behaviour observed. I prepared a leading- 

 off cover, which had a third lining in the middle of its length, and 

 determined the relation of the shock proceeding from the two 

 halves, both with small and great resistance in the experimental 

 circuit. In the latter ease, the circuit contained a tube 142 mm. 

 long, i '6 mm. wide, filled with distilled water, to which some 

 spring water was added. The bobbins of the galvanometer (12,000 

 turns) were obliged to be close up in order to obtain perceptible 

 deflections. The frog-interrupter worked with an overweight of 

 100 gr. in this and in all the following experiments, where it is not 

 otherwise stated. With only an instantaneous excitation, this 

 would correspond to about O-OI68" 1 , according to Helmholtz' 

 determinations ; but I have already before explained the reasons 

 why these determinations are not directly applicable 2 . The num- 

 ber of shocks indicated by the frog-alarum every time the cover 

 was put on, although always recorded in my note-book, is omitted 

 in the following tables, because when the frog-interrupter is used, 

 it makes no difference. 



1 Archiv fur Anatomie, etc., 1850, p. 325. 

 3 Ges. Abhandl., vol. i. pp. 226, 227. 



