OF THE CALABAR BEAN. 733 



occurs, again allows of a free circulation and of consequent paralysis of the 

 motor endorgans of the divided nerve. 



2. Afferent Nerve Fibres. 

 The discussion of the influence that those fibres in the spinal nerves that con- 

 duct impressions to the cord exert in producing paralysis, will be a short one, as it 

 can be readily shown that their effect is negative. It will be sufficient to notice that 

 in mammalians it was always possible to obtain evidence of their activity as long 

 as the functions of the spinal cord were retained, and that, therefore, they were 

 in no wise concerned in the production of the general flaccidity and loss of motor 

 power which is caused by Calabar bean. The same evidence was obtained in 

 frogs, and could in them be distinctly shown by localization of the poisoning. In 

 place of the function of these nerves being lessened, I believe that it is generally 

 increased, so that movements may be excited more readily after the action of the 

 poison than before it. 



Experiment XXXIV. 

 I tied the right ischiadic artery and veins of a frog weighing 573 grains, and suspended it 

 by the lower maxilla. Soon after, a silk thread was drawn over various parts of the skin, includ- 

 ing the right leg, without exciting any reflex movement. On dipping the feet, separately, into 

 dilute sulphuric acid (five minims of oil of vitriol to twelve ounces of water) reflex movements 

 occurred with each, after 80 beats of a metronome set at 100 in the minute. I then injected 

 into the abdomen two and a-half grains of extract in fifteen minims of water. In one hour 

 and three minutes, on the left foot being dipped into the acid, reflex movements occurred 

 in the right in 190 beats of the metronome; but no movement followed in the left limb in 200 

 beats, nor when the poisoned foot was placed in stronger acid (10 min. to 12 oz.), while this caused 

 energetic contractions of the non-poisoned portion of the right limb. The reflex activity of the 

 spinal cord was, therefore, very greatly diminished, and still the afferent nerves continued active. 

 The silk thread which was formerly employed was now drawn over the skin of the right leg 

 below the ligatures, and, as before, it produced no diastaltic movement. On applying it, however, 

 to the skin of the left leg and of the other poisoned regions, twitches constantly occurred in the toes 

 of the right leg, and only occasionally, and of a very feeble character, in the poisoned region. This 

 was repeated, at intervals, during the next ten minutes, with the same result. After this, the 

 thread ceased to excite diastaltic movements ; but the spinal cord had now lost its vitality, and 

 no movement could be produced even when it was directly galvanised. 



The afferent nerve fibres, in this experiment, retained their original activity 

 longer than the efferent, and at least up to the time at which they could not be 

 tested, because of the loss of the diastaltic function of the spinal cord. The 

 increase of excitability in the afferent fibres, where these had been acted on by 

 blood conveying physostigma, cannot be due, in the slightest degree, to any 

 spinal cause, for the effect did not occur in the right leg, to which access of the 

 poison had been cut off by ligature. Besides, measurement of the rapidity with 

 which reflex movements followed the application of a stimulus to either poisoned 

 or non-poisoned parts gave such proof of marked depreciation having occurred 

 before the afferent excitability had been increased as is sufficient of itself to 

 eliminate any spinal influence. 



