The beginning of the nineteenth century saw many revolutionary changes in medicine. The dermatologic subject which probably gave rise to the greatest controvery at the time was that embraced by the general term of parasitic diseases. Generations of conjecture regarding the cause of scabies ceased when Renucci, in 1834, first demonstrated Acarus scabiei at the Hôpital St. Louis. This was preceded by the amusing deception practiced by Gales in 1812; his organism proved to be the mite found in spoiled cheese. The modern knowledge of human ringworm infections dates from Schönlein's (1839) and Gruby's1 (1841) independent researches into the nature of favus.
Favus is not the only contagious parasitic disease of the scalp. There is another group of diseases designated as tinea tonsurans (teignes tondantes), or ringworm of the scalp, which have had a far more involved history than favus.
Space does not permit a detailed account of the