THE PHYSIOLOGY OF POISONING 185 



(5) Action upon the Nervous Centees. 



It is extremely difficult to determine with any degree of pre- 

 cision the nature of the lesions produced by venoms in the nervous 

 system. The intensity of these lesions depends in the first place 

 upon the length of time that has elapsed between the introduction 

 of the venom into the organism and death. It depends, secondarily, 

 in a large measure, upon the origin of the venom. That of the 

 Viperid^ acts almost exclusively upon the blood by coagulation, 

 and exhibits only a very slight degree of toxicity as regards the 

 nerve-cell. That of the Colubrid^, on the contrary, produces 

 manifest changes in the chromatic substance. Nissl's bodies are 

 completely disintegrated, and transformed into a granular mass. 

 In the majority of the stichochromes neither the form of the bodies 

 nor even the reticulum is distinguishable. The nuclei are opaque, 

 the nucleoli swollen and broken up. The dendrites often become 

 irregular and contracted (Ewing and Bailey,' G. Lamb^). 



It was found by Bailey that the majority of the cells of the 

 anterior cornua of the medulla are normal, but that a small number 

 of them exhibit indications of acute granular degeneration ; a few 

 cells were foUnd to have lost almost all their chromatic substance. 



From the physiological point of view it is perfectly clear that 

 Cobra-venom especially affects the bulbar centres, and particularly 

 the nuclei of origin of the pneumogastric nerve. We observe in 

 the first instance the gradual suppression of the functions vested 

 in the nerve-cells that are found in connection with the vagus 

 nerve, the spinal accessory, and the hypoglossal. Later on the 

 excitability of the nerve-endings in the muscles is found to have 

 been destroyed, and this action presents great similarity to that 

 of curare. 



The venoms of Viperid^, when injected in very weak doses, 

 exercise a paralysing action upon the reflex excitability of* the 



' Medical Record, September 15, 1900. 



' Lancet, January 2, August 20, October 22, 1904, and September 23, 1905. 



