CHEMICAL CONSTITUTION AND PHYSIOLOGICAL ACTION. 715 



Experiment LXV. — Having ligatured the sciatic artery and the two principal 

 veins at the middle of the right thigh in a frog weighing 195 grains, we injected 

 six-tenths of a grain of hydrochlorate of Dr Christison's conia, dissolved in four 

 minims of distilled water, under the skin of the left flank. In two minutes, stiff- 

 ness occurred in the anterior extremities. They gradually became curved in- 

 wards until the fore-paws were pressed against each other, and they were re- 

 tained in this position by tonic spasm, the frog having apparently no voluntary 

 control over them. Jumping movements could not now be accomplished, but 

 the frog pushed itself about by vigorous contractions of the posterior extremities. 

 In five minutes, there was marked weakness on the left posterior extremity, the 

 right remaining unaffected. In eight minutes, the stiff incurvation of the 

 anterior extremities had disappeared ; and, now, the animal was flaccid every- 

 where, except in the right posterior extremity. In nine minutes, irritation of 

 the poisoned skin was followed by barely perceptible twitches in the toes of the 

 left posterior extremity, and extremely vigorous movements of the whole right 

 posterior extremity. Occasionally, the right posterior extremity was extended 

 stiffly, and retained thus for one or two seconds, the movements presenting a 

 somewhat spasmodic appearance. In thirty minutes, the reflex contractions that 

 followed irritation of the skin were confined to the right posterior extremity ; and 

 the heart was now contracting at the rate of twenty-four beats in the minute. 

 In thirty -four minutes, the left sciatic nerve was exposed, the necessary dissection 

 causing vigorous movements in the right leg, and on stimulating the nerve by an 

 interrupted galvanic current, it was found that its motor conductivity was com- 

 pletely suspended, while its sensory (efferent) conductivity was retained ; no 

 movements occurring in the left posterior extremity, while energetic contractions 

 occurred in the right (non-poisoned) posterior extremity. The contractility of 

 the poisoned muscles was still unimpaired. Irritation of the skin in the poisoned 

 region excited reflex movements of the right (non-poisoned) posterior extremity 

 until two hours and fifteen minutes after complete paralysis had occurred in the 

 poisoned motor nerves ; but ten minutes after this, reflex movements could not 

 be excited. The frog did not recover from the poisoning. 



A considerable interval occurred, therefore, between the complete suspension 

 of conductivity in the motor nerves and the loss of the reflex function of the 

 spinal cord ; and, accordingly, it is evident that the condition of paralysis and 

 flaccidity caused by Dr Christison's conia is mainly dependent on its action on 

 the motor nerves. The experiment further shows that this paralysing action is 

 restricted, in the first place, at least, to the peripheral terminations of the motor 

 nerves. 



In the last two experiments, we have shown that certain slight spasmodic 

 symptoms are produced in frogs by conia. It is probable that these represent the 

 more violent convulsions that occur in mammals, and to which we have drawn 



