PRODUCED BY ATROPIA IN COLD-BLOODED ANIMALS. 475 



nerve, caused normal contractions of the left leg ; but when applied to the cut end 

 of its central portion, excited a violent tetanic paroxysm in which the left leg 

 took no part. 



Experiment LVII. differed from Experiment LVI. mainly in the nerve divi- 

 sion having been postponed until the tetanic stage was entered into. Before 

 the right sciatic nerve was divided, excitation caused a violent attack of tetanus, 

 during which the right posterior extremity was rigidly extended for eight 

 seconds. After the right sciatic nerve was divided, the right leg took no part in 

 the tetanic convulsions. Galvanic stimulation also of the cut end of the distal 

 portion of the nerve caused merely normal movements of the right leg. 



The symptoms of increased reflex excitability that occur so prominently in frogs 

 after the exhibition of certain pretty well-defined doses of atropia, are therefore 

 caused by a direct action of this poison on the spinal cord. 



Having reached this stage in the investigation, a\ e are naturally tempted to 

 proceed a step farther, and to inquire what is the nature of the action on the 

 spinal cord, by which atropia produces convulsive and tetanic symptoms ? At 

 first sight, the solution of this question might appear to be an easy one. Inves- 

 tigation has shown that atropia is a powerful agent in influencing the condition 

 of at least certain portions of the vascular system, although there is a difference 

 of opinion among investigators as to the nature of the influence. The probabi- 

 lities are, however, in favour of the view of Meuriot, that when large doses are 

 given, atropia first diminishes the calibre, and increases the vermicular contrac- 

 tion, of the blood-vessels ; and, subsequently, increases their calibre by para- 

 lysing the contractile walls.* It may be supposed that the latter effect — 

 dilatation of blood-vessels — is the cause of the tetanic symptoms ; for such 

 dilatation might operate either by permitting the augmented blood-supply that 

 many suppose to be essential for abnormal activity, or by causing irritation of the 

 cord directly, by congestion, or even rupture of its blood-vessels.f 



The plausibility of this view is strengthened by the opinion of so eminent a 

 physiologist as Brown-Sequard, who maintains that vascular dilatation is one 

 of the primary causes of the tetanic effects of strychnia;]; and by the post 

 mortem appearances of engorgement of the vessels of the spinal cord, after poison- 

 ing by atropia, which several observers have drawn attention to in mammals,^ 

 and which I have frequently observed in frogs also. 



There are, however, several grave objections to the adoption of a theory of the 



* De la Methode Physiologiqne en Therapeutique et tie ses applications a l'etude de la Belladone. 

 Paris, 1868, p. 51, &c. 



f Meuriot, op. cit. p. 98. 



J Lectures on the Diagnosis and Treatment of the Principal Forms of Paralysis of the Lower 

 Extremities. Philadelphia, 1861, pp. 51 and 112. 



§ Rosenberger, quoted by Tardieu, op. cit. p. 752; Schroff, Lehrbuch der Pharmacologic 

 Wien, 1868, p. 508. 



