CHEMICAL CONSTITUTION AND PHYSIOLOGICAL ACTION. 175 



We will now describe an experiment in which we endeavoured to determine 

 what portion of this system is affected. 



Experiment LXXIX. — The sciatic artery and the two principal veins were 

 tied in the right thigh of a frog, weighing 420 grains, and one-fifth of a grain of 

 sulphate of methyl-thebaium, dissolved in seven minims of distilled water, was 

 injected into the abdominal cavity. In six minutes, the animal was flaccid and 

 motionless, and in other four minutes the respiratory movements of the chest 

 and abdomen had ceased, while those of the throat continued, and did so for 

 several minutes longer. In sixteen minutes, galvanic stimulation by an inter- 

 rupted current, applied to any portion of the skin, caused movements of the right 

 leg below the points of ligature, but nowhere else. In twenty-one minutes, the 

 left sciatic nerve was exposed, and on galvanising it, energetic movements 

 occurred in the right leg, while the left leg and every other part of the body 

 remained motionless. The heart was now contracting at the rate of thirty-six 

 beats in the minute. The muscles that had been laid bare in the left leg, by the 

 dissection necessary for the exposure of the left sciatic nerve, were stimulated by 

 the direct application of an interrupted galvanic current, and they contracted 

 powerfully. This condition continued during other two days; on the second 

 day, even a feeble stimulus applied to the left sciatic nerve was followed by well- 

 marked contractions of the right leg, below the points of ligature ; while it caused 

 no movements in those parts of the frog that had been directly acted upon by the 

 poison, although the muscles everywhere contracted when directly stimulated. 



We learn from this experiment that sulphate of methyl-thebaium produces 

 paralysis by destroying the conductivity of the motor nerves, and not by inter- 

 fering with the function of the spinal cord, or of the sensory (afferent) nerves. 

 The next experiment was made with the view to determine what portion of the 

 motor nerve is paralysed by this substance. 



Experiment LXXX. — The left gastrocnemius muscle was exposed in the 

 leg of a frog, weighing 604 grains. The blood-vessels that entered it were 

 ligatured or twisted, and it was carefully separated from all its connections, 

 excepting that its origin and insertion were untouched, and that the nerve fibres 

 that entered it were not divided. Immediately after this somewhat tedious 

 preparation, one-fifth of a grain of sulphate of methyl-thebaium, dissolved in ten 

 minims of distilled water, was injected in the abdomen. Omitting the details 

 of the effects that ensued, it is sufficient to mention that, at thirty minutes 

 after this injection, the sciatic nerve was exposed in each thigh and galvanised, 

 with the result that in the case of the right nerve movements followed in the left 

 leg alone, and in the case of the left nerve movements followed in the left 

 leg, and there only. It was seen that these movements in the left leg were 

 entirely caused by contractions of the left gastrocnemius muscle, that is, of the 

 muscle which had been protected from the direct influence of the poison. 



VOL. XXV. PART I. 2 Y 



