SO-CALLED HABITUATION TO "ARSENIC"

¹ Pharmacological Laboratory, Bureau of Chemistry, United States Department of Agriculture, Washington, D. C.

No certain habituation of cats to "arsenic" fed in increasing doses at suitable intervals could be shown. The loss of appetite and slowness of eating which developed or which cats voluntarily induced, complicates an analysis of the data. This enables the cats to retain more food than they would had the meal been eaten at once and a portion subsequently vomited. This "pseudo" tolerance is not regarded by the authors in any sense as a real tolerance.

Cats fed daily doses of dissolved arsenious oxide ("arsenic") in sub-emetic concentration developed no habituation; on the contrary, they showed a decline in appetite. They vomited once or twice early in the experiments, obviously from the cumulative superimposition of the effects of the sub-emetic doses, and thereafter regulated the food intake, apparently to avoid the emesis.

The criterion of habituation has been the threshold emetic dose, which is much lower than the concentration necessary to produce immediate and complete emesis. The failure of cats to withstand such doses successfully is a fair criterion of the improbability of developing any noteworthy systemic or gastro-intestinal habituation to "arsenic" by feeding—the only manner in which habituation to "arsenic" has been claimed to have been produced in man or laboratory mammal.