57 



4th, That there is no proof that the pons varolii is the centre 

 of perceptions either of touch or of pain. 



5th, That if it is admitted that cries prove that there is a 

 perception of pain, we should have to admit that the medulla 

 oblongata is also a centre for these perceptions. 



XIX ON THE MODE OF ACTION OF SOME OF THE MOST ACTIVE 



POISONS UPON THE NERVOUS SYSTEM. 



Some of the results of my experiments on this subject have 

 already been published in the inaugural dissertation of my 

 learned friend and pupil, Dr. F. W. Bonnefin, with whom I per- 

 formed most of these experiments.* 



I intend to give here only the results of my researches on the 

 poisons which produce convulsions. For the sake of brevity I 

 have called them convulsing poisons. The most important 

 among them are : strychnine, brucine, picrotoxine, morphine, 

 digitaline, cyanhydric acid, nicotine, cyanide of mercury, sul- 

 phide of carbon, chloride of barium, and oxalic acid. 



The principal questions which I have endeavored to solve are 

 the following : 



1. What is the part of the animal frame upon which these 

 poisons act in producing convulsions ? 



2. By what mode of action do they produce convulsions ? 

 The parts of the body on which they could act are : 



a. The nervous centres. 



b. The motor or centrifugal nerves. 



c. The sensitive or centripetal nerves. 



d. The muscles. 



Of course, the convulsing poisons could act upon these four 

 parts together, or upon two or three of them. 



Now, as to the mode of action, these poisons could produce 

 convulsions directly or indirectly. 



In other words these poisons might act : 1. As excitants 

 either of the muscles or of the nervous system, and this is what 

 I call a direct action. 2. As causes of increase of the vital 

 powers of the muscles or of the nervous system, so that even a 

 slight excitation of these parts is able to produce convulsions, 

 and this is what I call an indirect action. 



* Rech. Experim. sur Faction convulsivante des priucipaux Poisons, in 4 

 Paris, 1851. 



