PREVENTIVE MEDICINE 265 



infected animals. In connection with this it should be observed 

 that the cases which are particularly dangerous are those in which 

 lesions are discharging, e.g., jaw lesions in cattle. In this way one 

 prevents the pus contaminating fields, common feeding boxes and the 

 like. Discharges should whenever possible be collected and 

 destroyed, and soiled litter should not be used as manure. Isolation 

 of cases should be accompanied by treatment with potassium iodide, 

 which in a longer or shorter period renders the animal safe. 



RINGWORM. 



This is a parasitic disease of the skin due to the pathogenic 

 fungi Dermatophytes or Dermatomycoses. Those producing skin 

 lesions in the domestic animals are classified as follows : Tricho- 

 phyia, Eidamella, Microspora, Achoria, Lophophyta (fowls) and 

 Oospora. 



Infection occurs by direct or intermediate contact, and the 

 spores or conidia are air-borne. The conidia retain their vitality 

 for a considerable time away from the body, and are not easily 

 destroyed by mild antiseptics. They settle on the skin, bud out into 

 hyphse which, rapidly branching and rebranching, form the web- 

 like mycelium; this in turn produces fresh spores in the terminal 

 sporangia or conidiophores. There is also a complicated sexual 

 propagation. As the growth of the fungus proceeds the 

 area of infected skin becomes depilated, prurius and erythema 

 set in with often slight secondary abrasions, the result of scratching, 

 biting, &c. The exudate which forms on the abraded surface 

 dries into a pinkish, sulphur-yellow, greyish, whitish, or even 

 violet-coloured crust according to the variety of the fungus present 

 and the animal host. Under this crust or scutula suppuration 

 sometimes occurs. The tendency of ringworm is to become 

 chronic in housed animals, but given no re-infection it will spon- 

 taneously disappear in 40 to 50 days in the horse and in 6 to 12 

 weeks in cattle. 



RINGWORM IN HORSES. Horses are affected by Microspora 

 and Trichophyta. The microspora affects foals and young animals 

 in the spring and early summer, and those that are kept housed for 

 considerable periods are especially susceptible. Once the animals 

 get out in the open and are exposed to the sun and wind recovery 

 spontaneously takes place. Trichophyta is found mainly on adult 

 horses that are herded together such as under conditions of war, 

 in dealers' yards, &c. Ringworm in the horse is very contagious 

 but readily yields to treatment. Microspora and trichophyta are 



