PRODUCED BY ATROPIA IN COLD-BLOODED ANIMALS. 485 



abscissa ot 2i is greater than the area enclosed by the curve s 4 s 8 , &c, and the 

 abscissa tj 20 . The symptoms are, accordingly, those of paralysis; the spinal- 

 stimulant action being so slight that its effects are not perceived. With small 

 doses of atropia, spinal-stimulant effects are more likely to be observed in 

 mammals than in frogs. If the minimum dose that produces paralytic effects be 

 determined, and then a series of doses gradually increasing from this be ad- 

 ministered, it will be found that in frogs a considerable increase may be effected 

 before any spinal-stimulant symptom is produced; but that in mammals an 

 extremely slight increase will cause spasmodic symptoms to make their appear- 

 ance. The explanation of this also is to be found in the propositions. 



It has thus been shown that the tetanic symptoms produced by atropia in frogs 

 are represented, though in a somewhat different form, in animals of a higher 

 development. Atropia, therefore, forms no exception to the general law that 

 poisons affect the same structures in the same way, in whatever animals these 

 structures occur. 



It has also been shown that the differences in the symptoms that are produced by 

 different doses in animals of the same species may be explained by the paralysing 

 action of atropia being greater than the spinal-stimulant. 



Paralysis, combined with spinal-stimulation, forms, therefore, the leading- 

 characteristic of the action of large doses of atropia on the cerebro-spinal nervous 

 system, and unless this combination be taken into account, which it has not 

 hitherto been, the symptoms that are produced by such doses cannot be rationally 

 explained. In the antecedent portion of this paper, and especially in section C, 

 this combined action on the nervous system has been demonstrated by a process 

 of physiological analysis. I now propose to add to this some further proof, 

 derived from what may be termed a process of physiological synthesis. 



So long as we are unable to separate from one another those elements or 

 groups of elements in atropia that produce its different effects— allowing that it 

 is legitimate to suppose that such elements or groups of elements exist — a strict 

 synthetical method cannot be applied to the investigation of its effects ; but an 

 imperfect synthetical method may be applied, in which we imitate these effects by 

 combining various substances of clearly denned action. For this purpose I have 

 selected strychnia, as the best known and most typical of the spinal-stimulants, 

 and sulphate of methyl-strychnium, as one of the simplest and, for such pur- 

 poses, certainly one of the most convenient of the paralysers of motor nerves.* 



It was found that a dose of strychnia, in the form of a salt, equivalent to 



* This action of sulphate of methyl-strychnium has been demonstrated by Dr A. Crum Brown 

 and the author in a paper read before this Society, and published in the Transactions, vol. xxv. 

 part i. pp. 151—203. I prefer this substance to curara, because of its strength being constant; and 

 on this ground I would recommend it to physiologists and physicians. 



VOL. XXV. PART II. G 1 



