34 



PROFESSOR C. R. MARSHALL ON THE 



the difficulty of avoiding mechanical stimulation of the mucous membrane by the 

 instillation. 



Moreover, as is evident from the experiments already summarised (Exps. IV., V., 

 VI., X., XL, XII.), the effect is still obtained after section of both fifth cranial nerves 

 in the base of the skull. And in one experiment in which these nerves were divided in 

 the interval between two injections the effect produced by the injections was similar 

 in both cases (fig. 8). 



It would therefore seem that the cause of the temporary paralysis of the respiration 

 is not to be found in stimulation of the nerve-endings in the nose. As previously 

 stated, it is in all probability due mainly to transient depression or paralysis of the 

 myo-neural junctions in the respiratory muscles. It has already been shown that 



Fig. 8.— Effect of tetia-niethyl-anunoiiium chloride before and after division of both fifth cranial nerves in decerebrate 

 rabbit. 12.12, right fifth nerve cut ; 12.13 left nerve cut. Letters as in previous figures, x |. 



greater or less paresis of the motor nerve-endings to the sterno-mastoid and the muscles 

 of the fore limbs occurs a few seconds after the injection of a dose of tetra-methyl- 

 ammonium chloride sufficient to paralyse the respiration. An examination of the 

 various experiments in which the effect on the respiration and the excitability of 

 the fore-limb muscles was observed shows that the paresis of the fore-limb muscles 

 is synchronous with the paralysis of the respiration. This is seen in fig. 1 in the 

 cessation of the spontaneous muscular movements, and also in fig. 2, although the 

 respiration in the latter case was not so quickly paralysed. It was further found 

 that the duration of the paralysis in each case was similar. After some injections 

 the limb muscles seemed to be more influenced than the respiration — a weak stimulus 

 which had previously produced a good contraction inducing for a short time no reaction 

 after a dose sufficient to depress, but insufficient to paralyse, the respiration : or, as 

 shown in fig. 1, failing to react to the same degree as before, after the respiration 



