The investigation of various fungi, called by French writers les champignons parasites , offers one of the most inviting fields of medical research. The rapid increase in the number of cutaneous lesions traced to fungous origin inevitably brings the dermatologist face to face with problems in mycology which clinicians have been accustomed to relegate to the botanist. While the science of bacteriology has developed rapidly as a branch belonging particularly to medicine, the study of true fungi has been generally considered as something of merely academic interest. Medical mycology has been lagging behind. Our schools give it scant notice and American literature deals with it only to the extent of detached case reports. So sparse, in fact, is our literature on the general subject of pathogenic fungi that I could not find a single complete description of the common thrush organism in more than a score of American text-books consulted for