In 1893 one of us published an account of an unusual condition of the scalp. He believed that the abnormality had not previously been described. In this opinion, however, he was mistaken, for as far back as 1884 Poggi had recorded a case. Since attention was first directed to the matter a few writers, English and foreign, have published cases and ventured on various but conflicting opinions in explanation of the facts observed. The last known contributor is Dr. Eugenio Bravetta, who communicated a paper to the Medico-Chirurgical Society of Pavia in 1910. It contains an account of three typical examples, and is useful in giving a list of published cases with their authors; but it is specially valuable because it epitomises the views of the various writers. As this communication of Dr. Bravetta is in Italian, a language not read by the majority of us, we venture to give, by way of introduction, a free translation and abstract.