Pathogenesis. 905 



but the infection has also been transmitted occasionally Ijy caressing a dog and by 

 skinning a slaughtered animal which had been affected with herpes. As a result 

 of such infection large outbreaks of the diseas^e have been noticed in man (especiaiiy 

 in soldiers). (In the year 1840, an endemic occurred in the Swiss village of Dor- 

 likou, whereby in a short time the greater part of the inhabitants were attacked, 

 but Gerlach states that it was due to sarcoptic scabies.) Tricophytia transmitted 

 to man produce an o])Stinate skin disease causing suppuration of the hair bulbs 

 (Gerlach, Bodin, Pusch, Friedberger and others). 



Pathogenesis. Herpes fungi infecting the skin grow into 

 the hair follicles and increase between the sheaths of the roots 

 and in the immediate parts; later on they surround the hair 

 roots completely and closely ; a delicate plexus of undivided and 

 segmented lilaments, and an enormous number of spores being- 

 formed, which surround the hair root like a mantel, and often 

 extend for some millimeters above the surface of the skin. Some- 

 what later the fungi grow through the hair roots upwards and 

 downwards, but the hair bulb remains uninvolved (Walsch). 

 The fungus also develops in the epidermis just under the horny 

 cell layer. 



After the localization of the fungus in the skin, the patho- 

 logical processes depend upon the virulence of the fungi, the 

 color and anatomical structure of the affected skin, and on the 

 variable susceptibility of the animals. On the sparselj'^ or downy 

 haired parts of the skin, the fungi growing within the epidermis 

 cause a superficial inflannnation with scant exudation upon the 

 surface of the skin and proliferative processes in the epithelial 

 layers, and besides an inflammation of the hair follicles and their 

 appendices, through which a nodule or vesicle forms, each cor- 

 responding to one hair, while in the region round about the 

 hair the inflammatory process causes reddening, possibly a 

 slight swelling, and always desquamation of the skin (herpes 

 tonsurans maculosus et vesiculosus). The irritation of the 

 nerve endings in the skin, which is due to the superficial inflam- 

 matory process, always leads to more or less intense pruritus. 



On the parts of the skin which are thickly covered with hair 

 the fungi increase in certain forms (generally microsporosis) 

 round about the hair roots, at first in the upper part of the 

 neck of the bulbus, and inside the hair root, and also in the epi- 

 dermis, whereupon the hairs split and become brittle, so that 

 they break off above the opening of the hair bulb (true herpes 

 tonsurans) ; in addition very small vesicles occur but soon dis- 

 appear, and scaling or desquamation persists (herp. tons, 

 maculosus). Itching is absent or only very slight. 



In the other and most frequent forms of herpes, on the 

 parts of the skin that are thickly covered with hair (herpes pro- 

 ducing baldness, tricophytia) which may also occur conjointly 

 with the form heretofore mentioned, the fungi growing in the hair 

 follicles cause folliculitis and perifolliculitis which is not in- 

 frequently purulent and varies in intensity; this loosens the con- 

 nection of the hair root with the hair follicle, and subsequently 

 the hair falls out completely; the hair follicle itself may at times 

 be destroyed and then baldness of the affected part of the skin 



