Relative Susceptibility of Adult and Young Mice to Asphyxiation

Abstract

It is generally stated that in carbon monoxide asphyxiation the smaller and the younger individuals, with the more active metabolism, tend to approach saturation more rapidly, and that small individuals therefore succumb sooner than large individuals. Four parts of carbon monoxide in 1000 parts of air are considered fatal to man after an exposure of less than one hour and presumably much more fatal to smaller animals such as mice.

Following the observation by one of us (R.C.A.) that the young of a family of wild mice survived while the parents died when exposed to illuminating gas, a series of experiments with 73 white mice was carried out.

The data in Table I show that, contrary to current belief, the younger survive longer. In pure concentrations of chemically inert gases (nitrogen, hydrogen and argon) the young survive exposures from 3 to 6 times as long as those which prove fatal to adults.

The lethal periods of exposure for adult and young mice, in the case of pure CO₂ and CO lie so close together that it is difficult to observe a survival of the young. This is partly due to the fact that when adult and young animals were simultaneously exposed the gassing was continued until all muscle twitching in the animal which succumbed first had ceased. The young in such cases were still alive when exposure to the gas was discontinued but died in air within a few minutes after the termination of the experiment. When the time of exposure is sufficiently shortened the young survive indefinitely and the adults die immediately after removal from the gas.

The difference in time of survival between adult and young in illuminating gas is even more pronounced than in the case of pure CO.