In 1901, during one of his oceanography cruises, Prince Albert the First of Monaco asks Paul Portier and Charles Richet to study the toxicity of small jellyfish fishing filaments (Coelentera). In the course of their work on the effects of a hypnotoxin extracted from various coelentera, they observe mortal accidents that are not a function of the dosage of the injections. Dogs that respond this way have all received a preparative injection, yet some dogs have no reaction to a second injection. In contrast the injection are activating when they occur more than 10 to 12 days after the first. This phenomenon is independent of the administered dosage, which may well be inferior to a toxic quantity. They call this phenomenon anaphylaxis, the contrary of protection, and analyze its primary characteristics. Paul Portier eventually returns to the Faculty of Sciences where he is Dastre's assistant. Charles Richer pursues research on anaphylaxis on his own in his laboratory at the Medical Faculty. By showing that an immune response could be pathogen as well as healing, these two scientists - who did not know each other before, working together for a few short months - made a discovery that opened up new venues in the growing field of medical immunology.