22 PROFESSOR C. R. MARSHALL ON THE 



movements of the limb were registered as in the previous experiment. Stimulation 

 with the secondary coil at 26 cm. produced a well-marked contraction, sometimes with 

 a slight staircase phenomenon. An injection of 1 mg. tetra-methyl-ammonium chloride 

 was made into the right facial vein at 12.3, and after preliminary convulsive contrac- 

 tions, produced paresis of the nerve-endings. Stimulation of the nerve at 12.7 with 

 the secondary coil at 26 cm. produced a simple muscle twitch. At 12.11, with the 

 coil at 22 cm., a slight sustained contraction was obtained, and at 12.19, with the 

 coil at 20 cm., the divided humped-back contraction shown at (a). The effect is 

 shown better at (b), the curve obtained by continuous stimulation of the nerve with 

 the same strength of stimulus at 12.21. 



The cause of the staircase phenomenon in tetra-methyl-ammonium chloride 

 poisoning has not been further investigated. It differs from that produced under 

 physiological conditions by adjusted repetitions of a stimulus in being preceded by a 

 well-marked rapid contraction which, in some cases, exceeds in height the summit of 

 the staircase, thus resembling in form the initial contraction and reflex rebound con- 

 traction observed on stimulating an uncut mixed nerve with a single induction shock* 

 and in the muscle requiring a much longer period of rest before it can be reinvoked. 

 As is seen in (a), a repetition of the stimulus fifteen seconds after the summit of the 

 staircase has been reached, is followed by no staircase phenomenon, and this is also true 

 if the stimuli are repeated at half-minute intervals. In this case the only observable 

 difference shown by each successive curve from that of the latter half of (a) is a more 

 rapid exhaustion. It is not until an interval of one to one and a half minutes between 

 the successive stimulations is allowed that the staircase effect begins to reappear. 



In one experiment the spinal accessory was isolated and stimulated intermittently, 

 along with the phrenic nerve, and the contractions of the sterno-mastoid muscle recorded 

 before and after injection of tetra-methyl-ammonium chloride. The effects obtained 

 were so similar to those observed in the case of the fore limb that further description is 

 unnecessary. 



In the case of a hind limb the effects observed after the injection of tetra-methyl- 

 ammonium chloride from stimulation of the sciatic or crural nerve are similar to those 

 occurring in a fore limb; but when the injections are made into the external jugular 

 vein the effects are less marked, and are later in appearing. Thus in a rabbit an- 

 aesthetised with ether the injection of 1 mg. tetra-methyl-ammonium chloride into the 

 external facial vein merely caused gradual diminution in the contractions of the hind 

 limb, produced by stimulation of the sciatic nerve, for two minutes, at the end of 

 which time only a slight twitch was obtained from continued stimulation. Eecovery 

 commenced one and a half minutes later, and was nearly complete six minutes after the 

 injection. The respiration, on the other hand, rapidly diminished in extent, and had 

 almost ceased eleven seconds after the commencement of the injection. It began to 

 increase ten seconds later, and was normal a minute after the beginning of the injection. 



*^Cf. Sherrington, Journ. of Physiol., xxxvi. p. 202 [1907]. 



