546 DISEASES OF THE HORSE. 



The organisms grow very slowly in the various culture media. It 

 requires about ten days before vegetation is noticed on agar in the 

 form of grayish-white granules, which gradually grow to larger 

 colonies, appearing considerably elevated and having a wrinkled 

 surface. They also grow in bouillon, in which a white, flaky deposit 

 makes its appearance after fifteen or eighteen days. In taking cul- 

 tures it is advisable to open a fluctuating abscess, over which the skin 

 should be shaved and well cleaned with bichlorid solution and alcohol. 

 The abscess should be opened with a sterilized scalpel, and culture 

 media may then be inoculated in the usual way. In case of a mixed 

 infection, the organism may be isolated by plating. 



The period of incubation varies greatly, extending from three 

 weeks to four months, or even longer. In artificial inoculations with 

 pus .through wounds in the skin, inflammation and swelling of the 

 lymph vessels may be noticed in twenty to sixty days, and these ves- 

 sels show in their course a development of hard nodules, from which 

 abscesses form. 



The natural infection is without doubt caused through superficial 

 wounds, such as galls, barbed-wire cuts, or through various stable 

 utensils, harness, bandages, insects, etc. Solipeds are mostly sus- 

 ceptible, but cattle may also be infected. 



Symptoms. — The inflammation of the lymph vessels is usually first 

 observed on the extremities, especially on one or both hind legs; it 

 may also appear on the forelegs, shoulder, or neck, and more rarely 

 on the rump, udder, and scrotum. The lesions, as a rule, develop in 

 the tissue adjacent to the place of inoculation. In the early stages of 

 the disease the lymph vessels appear very hard and thickened, and 

 along their course hard nodules develop, ranging in size from a pea 

 to a hen's egg. Later these nodules soften, burst spontaneously, and 

 discharge a thick,' yellowish pus. The surface of the resulting ulcers 

 or abscess cavities soon fills up with exuberant granulation which 

 protrudes beyond the surface of the skin, giving a fungoid appearance. 

 The affected extremities are considerably enlarged, similar to cases 

 of simple lymphangitis. In rare cases the mucous membrane of the 

 nostrils may also become affected, showing yellowish flat elevations 

 and ulcerations, and these may extend by metastasis to internal organs. 

 In cases where the mucous membrane is affected, the submaxillary 

 lymph gland may also become enlarged and suppurate. 



The constitutional symptoms accompanying this disease are not 

 very marked or may be altogether absent. There is usually only a 

 very slight fever, which seldom runs over 102° F. The appetite is 

 not impaired except in the. advanced cases. 



Lesions. — The anatomical changes are most marked in the skin and 

 the subcutaneous tissues. They may become 2 to 3 inches thick and 



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