I have made a number of experiments with a view to discovering whether the cerebral, bulbar, or medullary substance of animals susceptible to the action of Cobra-venom (rabbit, guinea-pig, fowl) possesses the property of _fixing_ this venom as it fixes the toxin of tetanus (Wassermann and Takaki). I found that, on pounding up a little of the pulp of the cerebral hemispheres or bulb with doses of venom lethal in two hours for the control animals, the injection of the mixture, well washed and centrifuged in order to free it from all excess of non-fixed venom, always caused death, but with a retardation of from four to ten _hours_. We see, therefore, that partial fixation of the venom upon the nervous elements really takes place, but we cannot conclude from this that these elements exercise an antitoxic function, any more than in the case of tetanus, for animals that receive cerebral emulsions in one thigh and the dose of venom lethal in two hours in the other thigh, succumb at the same time as the controls. Major Rogers has made similar experiments with the venom of _Enhydrina_ (HYDROPHIIDÆ), and has obtained the same result on employing the cerebral hemispheres of the pigeon.[27] Flexner and Noguchi,[28] on their part, have compared, by aid of the method of intra-cerebral injections, the toxicity of the venom of _Crotalus_ with that of the venom of the _Cobra_. On employing Cobra-venom heated to 75° C., they found that the convulsive and paralytic effects were immediate, contrary to what takes place after subcutaneous or intraperitoneal injections, but that the dose of venom necessary to produce death was the same (0·1 milligramme for the guinea-pig) as when the injection is made in the peritoneum or beneath the skin. With the venom of _Crotalus_ heated for half an hour at 75° C., which contains but very little _neurotoxin_ and has lost all its hæmorrhagic properties, 0·5 milligramme introduced directly into the brain of the guinea-pig only produces transitory and non-lethal effects; while, if fresh venom be employed, 0·05 milligramme is sufficient to cause death in three hours, with severe hæmorrhagic lesions. Now this dose is twenty times smaller than the minimal lethal dose for a subcutaneous injection. It is evident that the harmful matter, in the particular case of _Crotalus_-venom, is not the _neurotoxin_, but an altogether different substance, termed by Flexner and Noguchi _hæmorrhagin_, which acts upon the elements of the blood and upon the endothelium of the blood-vessels. We shall meet with this substance again in almost all VIPERINE venoms, and shall study it further on. CHAPTER VIII. _PHYSIOLOGY OF POISONING_ (_continued_). ACTION OF VENOMS ON THE BLOOD.