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condition arising after the invasion of the external mucous 

 membranes or cutaneous tissues by larvae of the genus 

 Habronema. It is believed that this term is more likely to 

 be correct than the term introduced by Railliet. 



F. General Summary. 



A granulomatous condition found most frequently affect- 

 ing the external mucous membranes of the horse in Southern 

 Australia has been found to be due to the presence of a larval 

 Nematode of the genus Habronema. These granulomata are 

 found less frequently on the sheath, limbs, and probably other 

 situations. The tissue reaction following the introduction of 

 the larva gives rise to a tumour presenting a characteristic 

 macroscopic and microscopic appearance. The larva is often 

 very difficult to demonstrate, and is only to be found in 

 lesions of up to about three weeks' duration. In lesions of 

 longer standing there is usually no evidence whatsoever of the 

 presence of the larva, but occasionally the spaces it once occu- 

 pied are to be seen. The larva is incapable of living in the 

 submucous, cutaneous, or subcutaneous tissues, and, therefore, 

 its presence in these tissues appears to be quite accidental. 

 Evidence suggests that these larvae are introduced from 

 without, and that they are deposited on moist surfaces during 

 the feeding operations of Musca domestica, which fly acts as 

 the intermediate host of both Habronema muscae and H. 

 megastoma. When deposited on the external mucous mem- 

 branes the larvae appear to be capable of pushing their way 

 through the membrane and of entering the submucosa. When 

 lesions occur on parts other than the external mucous mem- 

 branes, the moisture necessary to prevent desiccation of the 

 larvae appears to be most usually supplied by an exudation of 

 blood or serum. This would follow some injury to the skin of 

 the animal, either in the form of ordinary wounds or in the 

 form of small puncture wounds made by biting flies such as 

 Stomoxys calcitrant. 



After a consideration of the life-histories of the three 

 species of Habronema, it appears that the larva responsible for 

 the production of these lesions is most commonly that of H. 

 megastoma. It seems possible that the larvae of the other two 

 species may also cause similar lesions. The results obtained 

 by animal experimentation go to support these conclusions. 



The macroscopic and microscopic appearances of a granu- 

 loma commonly called "swamp cancer" which affects horses in 

 Northern Australia-are essentially the same as those found in 

 the granulomata occurring in Southern Australia. Evidence 

 suggests that this granuloma is possibly due to the larva of 



