MICROBIAL DISEASES OF MAN AND ANIMALS. 579 



The appearances of the disease differ in the various species of infected 

 animals, as also does the length of time it continues. The disease does 

 not affect the general health greatly, since it primarily attacks the drier 

 and more horn-like portions of the skin, but becomes conspicuous by the 

 falling of the hair and by the scabs or crusts with accompanying itching 

 and discomfort. Other species of the same genus have been described 

 which produce infected areas differing in detail but similar in their general 

 characters. 



FAVUS. Favus is caused by Achorion schonleinii, Remak, and affects 

 man, cats, dogs, mice, rabbits and fowls, and many wild animals. This is 

 characterized by crusts, thickened at the edges and somewhat cup-shaped 

 in center, composed of the mycelium of the mold cemented together into 

 masses by glairy substance. Below, these crusts are in contact with the 

 true skin. The fungus penetrates especially into the hair-follicles and 

 hairs themselves, which later are shed. It attacks different species of 

 animals with varying symptoms, but produces more serious lesions than 

 those of Trichophyton. Favus is especially serious as it attacks man. 

 Efforts to show that this fungus is merely a parasitic form of some species 

 of higher fungi have failed. The diseased conditions have become so well 

 denned and are reproduced so uniformly as to indicate a fixed habit in the 

 organisms, whatever its source or relationship. 



MISCELLANEOUS FUNGUS DISEASES.* 



SAPROLEGNIACE^ AND ENTOMOPHTHORACEyE.* Some of the Sapro- 

 legnias (all water fungi) form conspicuous masses of mycelium around 

 dead insects in stagnant water. Certain other species (Achlya sp.) cause 

 disease and death of fishes. The Entomophthoracece are parasites of in- 

 sects on land. One of these, Empusa muscce, destroys the common house- 

 fly, which, after death from this disease, is found attached by its mouth 

 parts to windows or woodwork. 



ENTOMOGENOUS FUNGI.* The practical usefulness of some of these 

 species, notably Sporotrichum globulifemm, as a chinch-bug disease, has 

 been studied carefully. While the work was markedly successful in caus- 

 ing an epidemic disease when conditions favored it, dependence upon 

 particular conditions was so complete that the production of the disease 

 as an effective destroyer of pests failed. Similar results have attended 



* Prepared by Charles Thorn. 



