652 RINGWORM. 



thereafter develops in the hairs, the hair follicles and the epidermis, 

 causing lesions which vary according to the species. 



At the present time three groups of ringworm are recognised as 

 occurring on animals, Trichophytic, Microsporous, and Favus. 



Clinically the trichophytons are divided into the T, ectothrix, which 

 lives outside the hair, and both outside and inside the hair follicles; 

 T. endothrix, which penetrates the thickness of the hair itself, render- 

 ing it brittle and easily destroyed ; and T. endo-ectothrix, which both 

 surrounds and invades the hair. 



The study of artificial growths of these fungi will probably afford 

 valuable information on the above points. In the ox the particular 

 parasite is invariably the Trichophyton mentagrophytes, whatever may 

 be the characteristics of the clinical lesion. 



In France ringworm is particularly common in Auvergne and 

 Normandy, where hygienic precautions are neglected, but cases may 

 also be found throughout the country. 



After affecting cows throughout the winter, the disease often dis- 

 appears in the spring. Throughout the winter cows are kept in dark 

 and often filthy sheds, where the parasite propagates rapidly, whilst 

 in spring they are sent to grass, where the conditions are inimical to 

 contagion. 



Diagnosis. The diagnosis of ringworm seldom presents any diffi- 

 culty. The appearance of the lesions (Fig. 266), their particular ten- 

 dency to spread and contagious character, facilitate the diagnosis. 

 They entirely differ from those of eczema or mange, and should any 

 doubt exist, the slightest microscopic examination is sufficient to dis- 

 sipate it. In ringworm in the ox the base of the hairs is covered 

 with enormous numbers of spore chains, which do not extend into the 

 depths. 



To detect the parasites it is best to shave off a thin fragment of 

 skin from the periphery of the patch, place it on a slide with a drop 

 or two of 30 per cent, caustic potash solution, and heat it for a few 

 seconds almost to boiling point. By applying a cover glass with 

 firm pressure the epidermal cells are spread out and the parasites can 

 be seen, especially around the roots of the hairs. Sometimes they 

 form little dirty -yellow masses, consisting almost exclusively of spores. 



When ringworm has attacked the entire surface of the body, it is 

 much more difficult to distinguish from sebaceous eczema, and a 

 microscopic examination or experimental inoculation may become 

 necessary. Inoculation with ringworm material always succeeds 

 with calves. 



Prognosis. Eingworm is not dangerous in itself. In time it may 

 disappear spontaneously, but when it extends over the whole body it 



