( 824 ) 



larger than the surface of a corpusculiim tactiis. The divergency 

 between the quantity of energy applied and that which is used for 

 reflex-stimulus is in this last case not by far so great as in the 

 thermal forms of reflex stimulus. The simplest relation might be 

 expected in the very favourable case already mentioned, in which 

 only one drop of mercury falling from a height of 7 cm. was used. 

 IMeauwhile, with the ball of resin, still smaller values were obtained, 

 notwithshxnding' the summation was taken into the account, so that 

 we may accept, this most simple case has not at all been a most 

 favourable one. 



§ 4. The electrical stimulation brought about by discharges of a con- 

 densator which was immediately before charged with a voltage varying 

 between and 2 volts. The capacity of the condensators, which were 

 constructed in the laboratory from mica of different thickness and cover- 

 ings of tinfoil dilferent in surface varied from 15 X ^0-^ to 4 X 

 10-3 m. p They were wholly closed in by paraffine and verified by com- 

 paring with an air-condensator. The following stimuli were used : 

 firstly on the skin of the leg of the frog by means of little catches 

 of steel wiiich surround the leg: secondly on the posterior roots of the 

 lumbal-cord, by means of platinum-electrodes set in paraffine, thirdly 

 on the ner\'us \'agus of a rabbit by means of platinum-electrodes set 

 in ebonite. The stimuli were for the greater part supplied in series 

 with an interval of Va sec. in a number varying between 1 and 15. 

 All those regulations took place automatically by properly isolated 

 swings and keys. The best results gave a condensator of 59X^0"^ 'n. F. 



Skinrefiexes (not ordened series) 

 (with condensator of .59.10— 5 m.F.) 



number of btimuli 

 number of observat. 

 0.65 0.62 jn. 67 average voltage 

 12.46 11. 341:!. 24'euergy in 10—4 



The above mentioned experiments were taken without a system. 

 Observing a more judicious succession of the stimuli more favourable 

 conditions of stimulation were obtained in the following series. 



From this table it distinctly appears that the stimulus is limited 

 to the smallest quantity of energy when a condensator 0,00035 m. F. 

 is used. Then 1,4 X 10"'* ergs is sufficient on condition that 

 the stimulus is repeated three times with an interval of Ys sec. 

 Consulting the experiments about reflexes which are not mentioned 



