424 Messrs. J. N. Langley and W. Lee Dickinson. [Nov. 21, 



lation of the sympathetic nerve in the neck than on stimulation of 

 the sympathetic fibres proceeding from the superior cervical ganglion, 

 it occurred to us that the action of nicotin might be due to a paralysis 

 of the nerve cells of the superior cervical ganglion, and not to a 

 paralysis of the peripheral endings of the sympathetic nerve. On 

 testing this view, by stimulating the sympathetic above and below 

 the superior cervical ganglion after injection of nicotin, we found that, 

 whilst stimulation below the ganglion produced no effect, stimulation 

 above the ganglion produced a dilation of the pupil and a constriction 

 of the vessels of the ear, as if no nicotin had been given. The effect 

 of stimulating the nerve fibres above the ganglion is not abolished by 

 an amount of nicotin four to five times as great as that sufficient to 

 abolish the effect of stimulating the sympathetic nerve in the neck. 

 This point, however, we shall consider more in detail in a later paper 

 upon the general action of nicotin. We are here only concerned 

 with the fact that after a certain dose of ?iicotin stimulation of the 

 sympathetic fibres below the ganglion does not produce dilation of the 

 pupil or constriction of the vessels of the ear, whilst stimulation of the 

 sympathetic nerve fibres above the ganglion produces these changes in the 

 normal manner. 



It is conceivable that the difference in the effect of stimulating 

 above and below the ganglion might be due to the nerve fibres being 

 medullated below and non-medullated above the ganglion, and to 

 nicotin paralysing the former and not the latter. But, in the first 

 place, although it is probable, it has not been shown, that the dilator 

 fibres of the pupil and the vaso- constrictor fibres for the ear are 

 medullated below the ganglion ; and, in the second place, it is obvious 

 that medullated fibres as such are not paralysed by nicotin, since for 

 some time after the stage in which stimulation of the sympathetic in 

 the neck fails to affect the pupil or the ear, stimulation of a nerve 

 such as the sciatic will cause movement both directly and reflexly, 

 that is to say, at this stage neither the medullated sensory fibres nor 

 the medullated motor fibres to skeletal muscle are paralysed. 



The method of action of nicotin can be tested in a more direct 

 manner. If the alkaloid produces its effect by acting upon the nerve 

 below the ganglion in consequence of any peculiarity of structure 

 obtaining there, the local application of nicotin to the nerve should 

 abolish its irritability. If, on the other hand, it produces its effect by 

 acting upon the nerve cells in the superior cervical ganglion, the 

 local application of nicotin to the nerve should have very little effect 

 upon the nerve irritability, but the local application to the ganglion 

 should abolish the effect of stimulating the nerve centrally of the 

 ganglion. 



In making the experiment on these lines, we isolate the sympathetic 

 nerve in the neck, the superior cervical ganglion, and to a certain 



