When under the influence of certain (or some) reasons (or causes) (alcohol, war, etc - added Spir here) the low instincts are unbridled (or unrestrained), the brute appears (or come forward, "apparait", Fr.) and rule over (or dominate), stifling every ("toute", Fr.) noble, generous impulse; it is then the ruin (or downfall or decline) of any humanity in man.