This is the old, old experiment that has been tried so many times in many diseases and has so often failed. It reminds us of the many attempts to confer on the tuberculosis patient the natural immunity possessed by the jackass by injecting the patient with the blood serum of that friend of man. The result of these experiments left some doubt as to who merited most the name of jackass, the doctor, the patient or the patient beast. Both pollantin and graminol have been praised highly in Germany but neither of them have succeeded so well in this country. Perhaps a shrewd advertising campaign had something to do with it; for the combination of a German scientist and his manufacturer can give points to any Yankee in exploiting the public with sure cures for the sick. =Active Immunity.= In active immunization, the real pioneers, after Mithridates, were the homoeopaths, who, for many years, have given small doses of poison ivy to prevent ivy poisoning and small doses of the poisons of infectious diseases to prevent and cure those diseases; but the homoeopath did not realize the transient nature of immunity and the necessity for continuing the treatment for many months or years, nor did he adopt the principle of increasing the dose to the point of toleration. The first to attempt active immunization and cure of hay fever by injecting extracts of the pollen that causes the disease appears to have been Noon, working in Wright's laboratory in London. The work was continued by Freeman, their work being reported in the _Lancet_, 1911, i, page 1572 and ii, page 814. They found the English spring form of hay fever due to the pollen of grasses. By dropping extracts of various pollens into the patient's eye, after the manner of Dunbar, they concluded that their patients were most sensitive to timothy grass and they used timothy extract exclusively in the treatment. Freeman states explicitly that a patient immunized against timothy grass is immune to all other grasses of that season; that it is unnecessary to immunize him to each particular grass, thus differing from some of our American observers who use the skin reaction to determine the particular pollens to which the patient is sensitive and inject every one of those pollens in the treatment. Independently of these British observers, Karl Koessler, of Chicago, in 1910, attempted to immunize patients against hay fever by injecting pollen extracts. Like Noon and Freeman, he used the eye reaction to test his patients and found them most sensitive to rag weed. Just as the Englishmen had used only timothy grass in their cases, Koessler used rag weed exclusively. His work is reported in his article on Hay Fever in Forchheimer's _Therapeusis_, Volume V and also in the _Illinois Medical Journal_, 1914, page 120.