THE PHYSTOLOGY OF POISONTNG 185 
(5) ACTION UPON THE NERVOUS CENTRES. 
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 
VIPERIDÆ 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 CoLUBRIDÆ, 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 25, 1905. 
