From a quantitative point of view it is especially the amount of poison actively assimilated which determines the effect. Every poison is without effect if assimilated in correspondingly small quantities. There is consequently a minimum poisonous dose, after which the poison begins to act; but this minimum dose can only be ascertained and specified when the qualitative properties and the weight of the organism are also taken into consideration; it has therefore a relative value. The strongest effect which a poison is able to produce is the destruction of the life functions of the organism, the fatal effect. This fatal dose, however, can only be determined relatively to the qualities of the organism in question. Not only is the absolute quality of the poison of decisive significance, but the degree of concentration often influences its action, that is to say, the greater or less amount of effective poison contained in the substance conveying it into the organism; concentration plays an important part in many industrial poisons, especially, as is obvious, in corrosive poisons. A further important point is the time which it takes to absorb the poison. The action of the poison—the whole expression of the symptoms of poisoning—is essentially influenced by this fact. Usually gradual and repeated absorption of small quantities produces slow onset of symptoms, while sudden absorption of larger quantities of poison brings about rapid onset of illness. In the former case the poisoning is called _chronic_, in the latter, _acute_. Acute industrial poisoning is sometimes so sudden that the affected person cannot withdraw himself in time from the influence of the poison, nor prevent its entrance in considerable quantities into his system; this is often caused by the fact that the effect of the poison is so rapid that he is often suddenly deprived of power to move or of consciousness, and remains then exposed to the action of the poison until help comes. Such accidents are mostly caused by poisonous gases. Occasionally also considerable quantities of poison enter quite unnoticed into the body, such as odourless poisonous gases in breathing, or poisonous liquids through the skin. In chronic industrial poisoning unsuspected accumulation of poison takes place, until symptoms of illness ultimately reveal themselves; as the first stages of poisoning are not recognised in time by the person affected, he continues exposed to the influence of the poison for weeks, months, even years, until the chronic effect has reached its full development and becomes obvious. Such insidious industrial poisoning arises through the continual absorption into the lungs or stomach of small quantities of poisonous dust, gases, and vapours, during constant or frequent work in an atmosphere containing such gases; poisonous liquids also, by soiling hands and food, or by penetrating the skin, can produce slow industrial poisoning.