PRODUCED BY ATROPIA IN COLD-BLOODED ANIMALS. 479 



ral, by which it produces paralysis, is, therefore, sufficient to account for the greater 

 readiness with which complete paralysis is produced in frogs than in mammals. 



It is thus seen why atropia produces paralysis so much more rapidly and 

 completely in frogs than in mammals, and also why in both frogs and mammals 

 spinal-stimulant effects are obviously manifested only when atropia is adminis- 

 tered in doses that are near the minimum fatal— that is, in doses containing the 

 largest amount of spinal-stimulant action consistent with the production of a 

 prolonged duration of symptoms. 



When a dose of atropia near the minimum fatal is given to a frog, paralysis 

 is caused with such rapidity and completeness, that the spinal-stimulant action 

 is at first prevented from exhibiting itself; but when a similar dose is given 

 to a mammal, paralysis is caused so slowly and incompletely that a sufficient 

 amount of reflex activity remains to allow the spinal-stimulation to manifest 

 itself by exaggerated reflex movements and convulsive spasms. In the frog, the 

 spinal-stimulation is, in the first stage, concealed by the impossibility of its effects 

 being manifested, and the first symptoms are, therefore, those of paralysis ; but, 

 as this paralysis is being recovered from, the spinal-stimulation becomes appa- 

 rent. In the mammal, the spinal-stimulation is merely impaired by the partial 

 paralysis ; and during the whole course of the poisoning, the symptoms are, 

 therefore, those of a paralysing combined with a spinal-stimulant action, the 

 former merely lessening the violence, without concealing the effects of the latter. 



This combined action, and the variety produced by it on the symptoms 

 in frogs and mammals, may be graphically illustrated by two curves, one of 

 which represents the paralysing, and the other the spinal- stimulant action. 

 The forms of these curves are to a great extent arbitrary, and they must of 

 necessity be so until we possess some exact method of estimating degrees of 

 action, and thereby obtaining ordinates that may have some pretension to 

 accuracy. Thus, in the curve op x p 2 &c, of Diagram 1, the motor nerve paralysis 

 is complete, so far as our methods of examination can show, atpc; but between 

 pc and p 2 there is a considerable interval, during which the degree of action may 

 or may not have been constant. What is termed complete paralysis does not 

 represent the maximum of action, for we know that the paralysis may go on 

 to permanent suspension of motility, or death, as well as return to normal 

 activity. As, therefore, the ordinates are but roughly determined, these curves 

 are in no sense accurate delineations of the paralytic and spinal-stimulant 

 actions. They may, however, serve the useful purpose of exhibiting clearly the 

 relations between the effects of these two actions. For the sake of simplicity, the 

 best marked paralytic action of large doses of atropia — that on the motor nerves 

 — will alone be considered. 



Diagram 1 is a delineation, on this plan, of Experiment XVI. of Table I. In 



