178 VEGETABLE PAEASITES. 



found between the upper extremity of the tunica internet of the 

 follicle and the epidermal sheathing of the hair; and the bulb 

 even disappears during the last period of the development of the 

 favus. 



According to Gudden, the imbedding of the favus in the hair 

 renders the latter white, rigid, brittle, and unravelled at the 

 point. The hair is opaque when examined immediately after 

 the addition of water, because the air which exists between the 

 longitudinal fibres and circular scales, or which is formed into 

 small vesicles, gives to the whole the appearance of a row of cells, 

 till it passes finally out by way of the circular scales on the side 

 collecting on the surface, and forming larger vesicles, which, 

 however, recede into these spaces as soon as the hair becomes 

 dried up. The hair becomes more transparent as soon as the 

 air has escaped, the greater portion of which is atmospheric ; the 

 smaller, perhaps, consisting of carbonic acid ; for some vesicles 

 are rapidly absorbed by the water, and little drops of oil are seen 

 floating about. 



Etiology of Favus. It is found in every age, mostly in 

 children. All modern writers agree that a scrofulous con- 

 stitution does not alone produce it, but that various diseases, 

 misery, privation, and unhealthy habitations, likewise foster it. 

 The sole cause of the favus is the transfer of the spores to the 

 skin, which may be effected in various ways. Few persons who 

 have daily to treat favus become themselves infected, and it may 

 therefore be well to presume, with Robin, that a predisposition 

 to it exists in the individuals attacked by this disease. It would 

 be more correct to say that contagion takes place only in the 

 case of open wounds, broken skin, &c., by which the spores of 

 the favus are attracted and developed. It is very doubtful 

 whether it is hereditary. It has not yet been thought worth 

 while to ascertain whether the children of parents who were 

 infected with favus had not come into contact with other favous 

 persons, and thus incurred the disease. Favi have only been seen 

 on the human skin. It is not known what kind of skin is most 

 advantageous to their growth. There is no reason why the favus 

 ought not to be considered as the primary cause, and not merely 

 as the bearer of a peculiar hypothetical favus-contagion. 



Reactions relating to the diagnosis of the favi and the epi- 

 dermal crustSy according to Bazin. Distilled water at the common 

 temperature, or boiling, rectified spirit, ether, and chloroform, do 



