Like other serpent poisons Crotalus seems to act primarily upon the cerebro-spinal nerve centers, producing secondarily decomposition of the blood, a destruction of blood fibrine, haemorrhages, ecchymoses, etc. (see Lachesis ). The most essential peculiarity of Crotalus is the similarity of its poisoning to that induced by yellow fever, in the treatment of which we find its chief use. Characteristic symptoms.