316 Dr. L. Rogers. On the Physiological [June 6, 



per kilo, weight, with a precisely similar result, including the presence 

 of the negative variation of the current of injury in each sciatic nerve. 

 In two more experiments doses of 5 and 1 milligrammes per kilo, 

 respectively were injected without previous ligaturing of a limb, and 

 in both cases stimulation of the nerves of each limb caused no muscle 

 response, although they contracted when directly stimulated. In each 

 case both nerves showed well-marked negative variation of the current 

 of injury, proving that their conducting powers were intact, so that it 

 is clear that the end-plates must have been paralysed. 



Action on the End-Plates of the Phrenic Nerves. 



The marked action on the motor end-plates of the poison of the 

 Enhydrina once more brings it into line with that of Cobra venom, but 

 on the other hand constitutes a marked difference from Pseudechis 

 venom, which C. J. Martin showed had no such action. He also found 

 that the stimulation of the phrenic nerves still produced normal con- 

 traction of the diaphragm after total cessation of respiration due to the 

 latter poison. 



In order to ascertain how far the paralysis of respiration produced 

 by Enhydrina venom is due to paralysis of the respiratory centre, and 

 how far, if at all, to poisoning of the motor end-plates of the phrenic 

 nerves, the following experiments were performed. 



Cat, weight 3J kilos., under chloroform. Tracheal cannula connected 

 with a recorder inserted. Left phrenic nerve exposed in the neck, 

 3J milligrammes of Enhydrina poison injected into external jugular 

 vein (1 milligramme per kilo.). Phrenic nerve stimulated by an 

 interrupted induced current at intervals of one minute. 



Occasional feeble inspirations produced by movement of the chest 

 walls only, continued up to the 24th minute, when they finally ceased. 

 At the 27th minute the final rapid fall of blood pressure to 50 mm. 

 took place. The sciatic nerves were tested at this point, and the right 

 when stimulated with the secondary coil at 30 mm. produced a good 

 muscular response, as did the left with the secondary coil at 27 J mm. It 

 appears from this that the phrenic nerve was paralysed completely before 

 any very marked loss of function of the sciatic nerves had taken place. 

 The respirations, however, were very greatly reduced in both frequency 

 and amplitude several minutes before any weakening of the phrenics 

 had occurred, so that the first and most important action of the poison 

 appears to be its effect on the respiratory centre, although the paralysis 

 of the phrenics speedily ensues and is a very important feature of the 

 action of the venom. If a very large dose is given, as in Experiment 5, 

 then the end-plates of the muscles in general are also paralysed at the 

 same time or very soon after the failure of the respiratory centre and 

 the phrenics. 



