It is extremely difficult to determine with any degree of precision 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,[25] G. Lamb[26]). 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 VIPERIDÆ, when injected in very weak doses, exercise a paralysing action upon the reflex excitability of the medulla. But it is open to question whether these effects are not exclusively due to the lesions of the blood, which are here all-predominant; for no histological modification is observed in the cells of the central nervous system.