CHEMICAL CONSTITUTION AND PHYSIOLOGICAL ACTION. 699 



exhibition usually failed to produce any serious symptom, even when so large a 

 dose as fifteen grains was given. In this experiment (Experiment XXIII.), the 

 symptoms were merely dilatation of the pupils with impaired vision, increase in 

 the rapidity of the cardiac and respiratory movements, diuresis and catharsis, 

 general excitement and slight spasms, and languor. In a few minutes, many 

 of these effects had disappeared, and the rabbit recovered perfectly. 



These experiments render it apparent that the action of the methyl deriva- 

 tives of atropia differs in several striking respects from that of the natural base. 



We have seen from Experiments XXII. and XXIII. that large doses of atropia 

 produce diuretic and cathartic effects in both dogs and rabbits, effects that are 

 universally recognised among the symptoms of atropia action. These are not 

 produced by the methyl derivatives. 



We have also seen, and our observations agree with those of many previous 

 experimenters, that when a salt of atropia is administered in a large dose to a 

 dog, the predominant symptoms are those of paralysis coexisting with convul- 

 sions. The experiments we have now described show that convulsions are never 

 produced by the salts of methyl-atropium, but that the predominating symptoms 

 of their action are those of paralysis alone. It is, therefore, obvious that by the 

 chemical addition of iodide or sulphate of methyl, some important change has 

 been effected in the action of atropia, by which its power to produce convulsions 

 has been removed. The determination of the exact nature of this change can be 

 conveniently effected only by experiments on frogs, for the causation of the con- 

 vulsive symptoms that appear in mammals has not yet been referred with 

 certainty to any special organ or structure. 



One of us has shown, in a paper published in this volume of the Transactions, 

 that when a dose of a salt of atropia near the minimum fatal is given to a frog, a 

 distinctly defined stage of paralysis is in the first place produced, which lasts for 

 many hours, or for several days ; and that this stage is succeeded by one in which 

 violent convulsive and tetanic symptoms are present. Further, it is demon- 

 strated in that paper that the convulsive and tetanic symptoms which charac- 

 terise the second stage, are due to an action of atropia on the spinal cord ; in fact, 

 to an action that may with propriety be likened to that of strychnia. From our 

 knowledge of these facts, we are enabled to examine if this strychnia-like action 

 of atropia is possessed by the salts of its methyl derivative. For this purpose, 

 we have made numerous experiments on frogs, of which the following are 

 examples. 



Experiment XXXVI. — Two minims of a solution of two-tenths of a grain of 

 sulphate of methyl-atropium, in forty minims of distilled water, was diluted with 

 two minims of distilled water, and the four minims of solution thus obtained, 

 containing one-hundredth of a grain of sulphate of methyl-atropium, was injected 

 under the skin of a frog, weighing 230 grains. In six minutes, the frog had 



