220 LEECHES 



Stimulate the tissues to renewed growth-activit_y. In Florida 

 the disease affects on])- the genus equus." 



§ 171. History. In 1896, some of the diseased tissue 

 from cases of this affection, in Florida, were sent to the 

 Bureau of Animal Industry for investigation. They were 

 studied by Dr. P. A. Fish who made an extended report on 

 the results of his findings. He also gave a verj- complete 

 review of the literature. 



A summary- of the literature shows that among the old 

 theories "Leeches" was believed to be a blood disease in many 

 ways not unlike syphilis, scrofula and farcj'. The "fly 

 theory" of the causation and dissemination of bursattee was 

 entertained by the natives of India as early as 1S20. Jackson, 

 m 1S42, seems to have been the first to believe that there was 

 any connection between the disease and a fungus. 



Hodgson, in 1853, referred to the sores as cancerous ulcers 

 and Hart in 1872, was strongly inclined to pronounce it 

 cancer, although he could not confirm this view structurally 

 by microscopic examination of the tissue. It seems to be 

 generally accepted that the disease is peculiar to the Tropics, 

 but cases have been reported in Kansas and Minnesota in the 

 United States, not only during the summer months, but when 

 the thermometer registered below zero. We might also expect 

 that the disease would exist in Mexico and Central and South 

 American countries, where the conditions of temperature and 

 moisture are favorable. 



Reports show that a high temperature is essential for the 

 development of the disease, although exceptional cases are 

 noted as occurring during the cold season. ^Moisture does not 

 seem to be necessary, since many cases develop when the 

 season is dry. It is, however, an important factor. Statistics 

 show that cases are more numerous and that the disease 

 assumes a more aggravated form during the wet season. 



In India, native as well as foreign bred horses are sus- 

 ceptible, but according to some writers, none of the other 

 equine species are affected. 



In the United vStates mules and cattle are said to develop 

 it, but not as readil}' as the horse. Outbreaks among cattle are 



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