In order to demonstrate the presence of the limnophysalis in the blood of patients affected with intermittent fever during the febrile stage, properly speaking, it appeared necessary for me to dilute the blood of patients with a solution of nitrate of potassa, having at 37.5°C. the same specific gravity as the serum of the blood. With capillary tubes of glass, a little dilated toward the middle, of the same shape and size as those which are used in collecting vaccine lymph, I took up a little of the solution of nitrate of potassa above indicated. After this I introduced the point of an ordinary inoculating needle under the skin, especially in the splenic region, where I ruptured some of the smallest blood-vessels of the subcutaneous cellular tissue. I collected some of the blood which flowed out or was forced out by pressure, in the capillary tubes just described, containing a solution of potassa; after which I melted the ends with the flame of a candle. With all the intermittent fever patients whose blood I have collected and diluted during the febrile stage, properly speaking, I have constantly succeeded in finding the Limnophysalis hyalina in the blood by microscopic examination. It is only necessary for me to mention here that it is of the highest importance to be able to demonstrate the presence of fungus in the blood of the circulation and in the urine of patients in whom the diagnosis is doubtful. The presence of the Limnophysalis hyalina in the urine indicates that the patient is liable to a relapse, and that his intermittent fever is not cured, which is important in a prognostic and therapeutic point of view. When the question is to prevent the propagation of intermittent fevers, it is evident that it should be remembered that the Limnophysalis hyalina enters into the blood by the mucous membrane of the organs of respiration, of digestion, and the surface of the pulmonary vesicles. We have also to consider the soil, and the water that is used for drinking.