1906.] 



Special Excitable Substances in Cells. 



185 



The preceding argument has been based chiefly on the fact that nicotine 

 excites certain muscles in the fowl, as well as abolishes, when given in 

 sufficient amount, the effect of the nerves upon them. 



Now, as mentioned already, nicotine abolishes motor nerve action in all 

 vertebrates investigated. It would be very remarkable if the stimulating 

 action occurred only in birds. I have not made any systematic investigation 

 of the question, but, in thinking about it, I remembered that v. Anrep* had 

 described catalepsy of the fore limbs of the frog as being caused by nicotine 

 after destruction of the spinal cord and that the phenomenon had been 

 confirmed by Dickinson and myselff and additional details given. 



The tonic contraction produced in the muscles of the fore limb of the frogj 

 is clearly similar to, though not identical with, that produced in the gastroc- 

 nemius and other muscles of the fowl. Its duration, however, may be much 

 greater. The effect is to cause the fore legs to be drawn over the sternum in 

 the manner described by early observers, who, however, did not definitely 

 attribute it to peripheral stimulation. 



An illustration of the effect of nicotine on the fore limbs is given in fig. 7. 

 The brain and spinal cord of a frog were destroyed ; in this state the muscles 

 are, of course, flaccid, and the limbs if raised and let go. at once fall. The 

 frog was placed on its back with the fore limbs by the side of the body. 

 Then a little 1 per cent, nicotine was injected into the abdominal cavity ; this 

 caused the assumption of the position shown in fig. 7. 



Fig. 7. — Frog. Killed by destroying the whole of the central nervous system. Con- 

 traction of the muscles of the fore limbs caused by nicotine. 



If a graphic record of the movement of the limb is taken, it is seen that the 



tissues of vertebrates which he quotes seem to me, as to many others, without exception 

 inconclusive. Of the tissues of invertebrates I have but slight experience. 



* v. Anrep, 'Arch. f. (Anat. u.) Physiol.,' 1879, Supp., pp. 167, 209. 



t Langley and Dickinson, ' Journ. of Physiol.,' vol. 11, p. 265, 1890. 



% Most of my experiments were made during the breeding season, when.' it is possible 

 that the tendency to tonic contraction is greater. 



VOL. LXXVIII. — B. n 



