702 DRS CRUM BROWN AND FRASER ON THE CONNECTION BETWEEN 



under the skin at the right flank of a frog, weighing 461 grains. The usual 

 paralytic symptoms very quickly supervened ; and in seven minutes and thirty 

 seconds, it was ascertained by galvanic stimulation that the motor conductivity 

 of the sciatic nerves was suspended, while muscular contractility was retained. 

 On the following day, this condition of the motor nerves and of the muscles con- 

 tinued, and the heart's contractions were found to be occurring at the rate of 

 thirty in the minute. On the third day, the body was slightly rigid, galvanism 

 of the nerves and muscles caused no contraction, and the heart was motionless. 



Similar experiments were made with iodide of methyl-atropium, and no con- 

 vulsive symptoms were produced by this salt. It was found that its poisonous 

 activity for frogs is less than that of the corresponding sulphate, though consider- 

 ably greater than that of sulphate of atropia, being equivalent to the ^^jgth of 

 the frog's weight. Short details of these experimeuts will be found in the 

 Tabular Summary. 



Having thus determined, by our experiments on dogs, rabbits, and frogs, that 

 the salts of methyl-atropium do not possess the convulsant action of atropia, it 

 is important that we should next ascertain by what action the paralytic s} 7 mptoms 

 of the salts of methyl-atropium are produced. Before doing this, however, it 

 may be of advantage to show in what manner atropia itself produces paralysis. 



The mechanism of the paralytic action of atropia is a complicated one, for 

 there is good reason to suppose that it consists of actions on the sensory and 

 motor nerves, and probably, also, on the spinal cord.* The following experiment 

 illustrates the order in which several of these actions are produced. 



Experiment XXV. — The sciatic artery and vein were ligatured at the upper 

 part of the right thigh of a frog, weighing 215 grains; and, a few minutes after- 

 wards, one-fourth of a grain of sulphate of atropia, dissolved in four minims of 

 distilled water, was injected under the skin at the left flank. In eight minutes, 

 a slight degree of paralysis was present, but the frog was able to perform some- 

 what imperfect jumping movements until thirty- five minutes. In forty minutes, 

 however, it lay flaccid on the abdomen, with the head resting on the table, and, 

 now, irritation of the skin of any region caused no other effect than a number of 

 pretty vigorous movements in both posterior extremities, of rather greater energy 

 in the non-poisoned (right) than in the poisoned. These reflex contractions could 

 likewise be excited by gently touching the skin, in the poisoned as well as in the 

 non-poisoned regions. The heart was now contracting at the rate of twenty-six 

 beats in the minute. With the exception of a gradual diminution in the rate of 

 the heart's contractions, no notable change occurred in the state of the animal 

 until one hour and twenty minutes after the injection. At this time, gentle 



* Authorities differ somewhat in their interpretation of the relations of these actions, some con- 

 sidering that the motor nerves are paralysed more rapidly than the sensory (Botkin, &c), and 

 others that the sensory are paralysed more rapidly than the motor (Lematxre, Meuriot, &c). 



