PRODUCED BY ATROPIA IN COLD BLOODED-ANIMALS. 489 



At the same time, the last experiment is in all respects a satisfactory one, for 

 it clearly demonstrates that such a combination of a paralysing with a spinal- 

 stimulant substance as produces in frogs paralysis followed by convulsions, will 

 produce in mammals paralysis coexisting with convulsions, and impeding their 

 manifestation. So that by a process of what may be termed physiological 

 synthesis, further evidence has been obtained in support of the conclusions, that 

 the effects of large doses of atropia on the cerebrospinal nervous system {mental 

 phenomena excluded) are due to combined spinal-stimulant and paralysing actions 

 of that substance, and that the differences in the relations of these effects to each 

 other, which are seen in different species of animals, may be explained by this com- 

 bination acting on special varieties of organisation. 



It is generally admitted that atropia produces both paralytic and convulsive 

 symptoms in mammals, but no satisfactory attempt has hitherto been made to 

 define the relations of these symptoms to each other. This investigation has 

 shown in what manner the paralysing is related to the convulsant action both in 

 mammals and in frogs; and it has also accounted for the differences in the mani- 

 festation of these actions after different doses of atropia. It may, without pre- 

 sumption, be asserted, that it throws a new light on the causation of some of 

 the symptoms of atropia, and also of many other substances, whose action, like 

 that of atropia, produces a combination of paralytic and convulsive symptoms. 



The principal results that have been obtained may be thus summarised : — 



1. Atropia produces in frogs well-marked convulsive and tetanic symptoms, 

 which, when present in an extreme degree, form a separate stage in the poisoning, 

 succeeding that of paralysis. 



2. Tetanic symptoms follow the subcutaneous administration of a dose of 

 sulphate of atropia, equivalent to the x J- th of the weight of the frog, and of 

 doses a little greater or less than this. 



3. These symptoms are due to a direct action of atropia on the medulla 

 (oblongata and spinalis). 



4. The differences between the paralytic and convulsive symptoms that occur 

 in frogs and those that occur in mammals may be explained by the greater sus- 

 ceptibility of the former to the action of a paralysing agent, and by the amount 

 of paralysing being greater in atropia than the amount of convulsant action. 



5. The different symptoms that are produced by different doses of atropia in 

 animals of the same species may be explained by its paralysing being greater 

 than its convulsant action. 



6. The paralysing and convulsant actions of atropia can be imitated in both 

 frogs and mammals by a combination of a paralysing with a convulsant sub- 

 stance. 



VOL. XXV. PART II. 6 K 



