OF THE CALABAR BEAN. 731 



Experiment XXX. 

 A similar experiment was performed on another frog, also poisoned with two grains of 

 extract, but weighing only 464 grains. 



a. Examination of the Nerves (two hours and twenty minutes after the injection). — The 

 galvanic current was passed along portions of both sciatic nerves simultaneously. "When 

 the secondary coil reached 52°, the non-poisoned gastrocnemius was thrown into tetanus, 

 the poisoned remaining inactive. It was then slowly advanced ; and at 30°, faint contract 

 tions occurred in the poisoned gastrocnemius, of a partial character, as if only a few muscular 

 bundles, and not the whole muscle, were contracting, and which continued for a few seconds 

 only, and did not recur although the secondary coil was advanced, after an interval for rest, to 

 0° (the strongest current from this arrangement). The stimulus was then applied to the trunk 

 of the non-poisoned nerve above the position of the ligatures, and, therefore, where it must have 

 been in contact with the poison ; contraction again occurred when the secondary coil was at 52°. 



b. Examination of the Muscles. — When the secondary coil reached 55°, tetanus was 

 produced in the poisoned gastrocnemius ; and at 54 0- 5, the non-poisoned muscle was thrown 

 into tetanus.* 



It would thus appear that motor nerve excitability or conductivity is diminished 

 and then destroyed by physostigma (this change being produced at the endorgans), 

 while retained for a long time thereafter in those parts of the same animal which 

 have been guarded from the access of the poison. It is also seen that the effect 

 on idio-muscular contractility is exactly converse; that property being uninjured 

 by the mere presence of physostigma, while diminished and destroyed by stoppage 

 of the circulation. 



It is usually asserted that division of a nerve, previous to the exhibition of 

 any substance that affects its vitality, is a sufficient method for determining 

 the position of its primary implication, and, therefore, sufficient for determining 

 the direction in which this extends. This proceeds upon the supposition that 

 when it is the nerve trunk near its origin that is first affected, extension of the 

 poisoned condition to the distal portion will be delayed by intermediate division of 

 the nerve. Bernard attempts in this way to prove that the primary paralysis of the 

 motor nerve endorgans by curare extends from them, along the trunk of the nerve, 

 towards the cord.t The paralysis of the motor nerves after strychnia is said to 

 proceed in a direction exactly the reverse, — from the origin to the periphery.! 

 It appeared of some interest to examine this question with Calabar bean, for with 

 it we would not expect that previous division of the trunk should delay the 

 implication of the nerve endorgans, as this precedes the paralysis of the trunk. 



Experiment XXXI. 

 I exposed the two sciatics of a frog for a short distance, and both equally, and divided the 

 left nerve with a very sharp pair of scissors. A fatal dose of Calabar bean was then administered. 

 When reflex movement could no longer be excited (one hour and two minutes after the ad- 

 ministration), the right sciatic was galvanised ; but no contractions were caused. The left was 

 stimulated, at the cut extremity of its distal portion, with the same current, and active move- 

 ments of the left leg and toes followed. The galvanism was repeated, at intervals of five minutes, 



* In Experiments XXTX. and XXX. I have thankfully to acknowledge the valuable assistance 

 I obtained from Dr Rutherford. 



■f- Loc. cit., p. 312. J Ibid. 



VOL. XXIV. PART III. 9 N 



