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



comparatively little, that, if in the above experiment nicotin 1 pei' 

 cent, be copiously applied to the vagus or to the ganglion trunci vagi, 

 the inhibitory power of the vagus upon respiration is apparently 

 unaffected. 



Although in an experiment condncted in the manner just described 

 there is little or no diminution of irritability of the sympathetic nerve 

 on applying 1 per cent, nicotin to it, repeated application of nicotin 

 to the nerve does, as might be expected, lower and finally destroy its 

 irritability. And if the nerve is ligatured and a long piece isolated 

 so that the blood supply to it is cut off, a great reduction or even 

 abolition of irritability takes place on soaking it with 1 per cent, 

 nicotin. But, with proper precautions, the difference in the effect of 

 applying nicotin to the ganglion and to the nerve is so great that 

 there is practically no danger of confusing the action on the cells 

 with that on the nerve fibres. In the nerves of the frog, the effect 

 on the nerve fibres, other things being equal, has^ seemed to us to 

 be greater than in the mammal. Since nicotin is alkaline, it is possible 

 that a part of its injurious effect may be due to its alkalinity. And 

 in fact, if a 2 per cent, solution of nicotin be neutralised with sulphuric 

 acid, and diluted with water so that it contains 1 per cent, nicotin, 

 its effect both upon nerve fibres and upon ganglion cells is lessened. 

 This is especially the case with nerve fibres. The cervical sympathetic 

 may be left for a minute or two in a pool of 1 per cent, nicotin 

 sulphate,* and still on stimulation cause maximum dilation of the 

 pupil. The superior cervical ganglion requires a freer application of 

 1 per cent, nicotin sulphate than of 1 per cent, nicotin to paralyse it, 

 but the paralysis is still readily produced. The period of paralysis, 

 after painting the superior cervical ganglion with 1 per cent, nicotin, 

 passes off in twenty to thirty minutes, so that in no long time the 

 sympathetic in the neck produces its usual effects. 



To paralyse the ganglion a second time requires a very much 

 larger dose of nicotin than was required the first time. Painting 

 it over with even 0'5 per cent, nicotin without any excess of fluid may 

 be sufficient the first time, but painting the ganglion half-a-dozen 

 times with 1 per cent, nicotin may be required to paralyse it a second 

 time. We had hardly expected to find so marked an example of the 

 habituation to poisons which is known to occur in certain cases, and 

 especially with nicotin. Apparently also the period of paralysis lasts a 

 shorter time after the second application of nicotin than after the first. 



A« a rule, the application of nicotin to the ganglion causes for a 

 brief period the same effect as stimulating the nerve. The alkaloid 

 appears to excite the nerve cells before paralysing them. 



* For convenience we speak of the neutralised solution containing 1 per cent, 

 nicotiu as a 1 per cent, nicotin sulphate solution. It contained, of course, a r.ither 

 higher percentage of the sulphate. 



