This paper outlines a phenomenological approach for describing physiological reactions occurring immediately after vital threats. This exemplified by data taken from previous studies relative to chemical intoxications of rats by a neurotoxical drug. The survival rate of the animals and the variations of their cerebral acetylcholinesterese activity are both reported as a function of the drug concentration, and with respect to their age. The collecting of the results may be described as the cusp, a bifurcation set of Thom's Catastrophe Theory.The (...) young animals react by a vital burst which modifies the shape of the cusp. A new fold or pocket takes place, changing it to the butterfly bifurcation set. This pocket supports the survival attractor concept, which appears reactional, transitory and variable in its intensity. (shrink)