The preventive treatment of autumnal hay-fever by means of desensitization is lacking in uniformity. Scheppegrell1and his followers have for years advocated simplicity in the treatment of hay-fever. Thus, he has divided the hay-fever pollens into four groups, and has expressed the belief that a pollen extract made from any member of a group would be applicable to other members of the same group. According to this view, a pollen extract of the short ragweed may well be employed for the prevention of hay-fever caused by the giant ragweed,Gaertneria, IvaorXanthiu[ill]. Commercial establishments have complicated the situation by encouraging the use of a mixture of pollen extracts, derived from the short and the giant ragweeds, from goldenrod and from corn. Still more complex has the matter of prophylaxis become through the practice of desensitizing the patient against several of the pollens that have yielded positive skin reactions.