506 DISEASES OF THE SKIN. 



do not take root very readily ; hence the transfer of a mass of such 

 spores from one person to another by no means invariably results in a 

 transplantation of the disease. However, the cases in which a healthy 

 person has been thus infected artificially are numerous enough to place 

 the fact beyond a doubt that the growth of the fungi is no mere accident, 

 but that it is an essential condition of the disorder. Whence the seeds 

 of favus have come, cannot, in many instances, be determined ; but I 

 believe that the enormous multitude of sporules of different kinds 

 constantly floating in the atmosphere will always afford opportunity 

 for the implantation of favus, and that such implantation will always 

 take place whenever conditions favorable to the growth of the germ 

 present themselves. Opinions differ as to whether or not the favus- 

 plant is a peculiar species of fungus which only appears upon the scalp 

 and which always develops in the same manner. Hebra inclines to 

 the view that the various shapes presented by the skin-diseases due to 

 the presence of vegetable organisms, depend rather upon the stage 

 of development of the plant, upon whether the spores preponderate over 

 the filaments, and upon whether the parasite take root upon the epi- 

 dermis or upon the hairs, and that it does not depend upon any spe- 

 cific difference of species in the spores themselves. I have this objec- 

 tion to make against this opinion : that, to the best of my belief, com- 

 plications of these diseases, and transitions of pityriasis versicolor, 

 with favus or herpes tondens, never occur, and that complications of 

 favus and herpes tondens are rare. These facts make it improbable 

 that the differences between these parasitic diseases are mostly due 

 to differences in the situation and stage of development of the 

 same fungus. The most simple explanation of the exceptional cases 

 is, that sometimes the favus and herpes fungi are transplanted simul- 

 taneously to the same individual. According to the researches of 

 Hofmann of Giessen, who has cultivated the fungus, it is identical with 

 the mucor racemosus, and is sometimes accompanied by the penicil- 

 Hum glaucum, but only as an accidental occurrence. Dirt seems to be 

 the condition most favorable to the implantation and growth of the 

 germs of favus ; at all events, the disease is far more common among 

 the lower classes, whose members often neglect to wash and comb 

 themselves, than among the well to do, among whom the appearance 

 of favus is exceptional. 



SYMPTOMS AND COURSE. The seat of favus is aimost exclusively 

 upon the hairy portions of the scalp, and it is rarely found in other 

 situations. At the commencement of the disease we find the affected 

 skin studded with small yellow oodies, scarcely of the size of a pin's 

 head, which lie somewhat embedded in the skin, and each of which is 

 perforated by a hair. These bodies consist of masses of spores, which 



