Abstract

On intravenous injection protein precipitation may occur intravascularly. This phenomenon must be considered in the interpretation of such experimental data. Zinc, calculated as the metal, is about equally toxic for all species studied (rats, rabbits, cats and dogs). Cadmium is about three times more toxic to cats and dogs, but to rabbits and rats four or five times more toxic, than zinc.

Subcutaneous administration furnished little information of interest because of the protein precipitation at the site of injection and poor absorption.

On oral administration the lethal dose of zinc is from five to seven times greater than that of cadmium. In dilute solutions used, cadmium is more toxic than in more concentrated solutions.

In the case of animals that vomit, such as cats, the chief effect of the oral administration of cadmium and zinc salts is emesis, which is dependent upon the concentration in which these substances are present in the gastric contents. This local effect varies with the character of the food, being more powerful when the metals are administered in diets of liquids than when administered in those of raw hashed, lean meat. The consumption of an average-sized meal of raw hashed meat containing 350 to 400 parts per million of cadmium or 3000 parts per million of zinc is almost always followed by emesis. Cadmium calculated as the metal is eight to nine times more effective as an emetic than zinc.

The results of continued cadmium feeding experiments agree remarkably well with the data obtained in the vomiting experiments. Concentrations of cadmium of 250 or more parts per million in the diet were incompatible with life. This is also the mean emetic concentration. Recovery followed reduction of this concentration. No evidence of cumulative systemic action was obtained in these experiments. However, slight loss of appetite, nibbling of food and occasional vomiting indicate that, although apparently compatible with life, the presence in the food of the lower concentrations tried is decidedly objectionable.

No evidence of storage of cadmium other than in the kidney, liver and spleen was obtained. The kidney usually contained the most metal relatively, while the spleen contained the least and sometimes none.