123 



of the condition being due to some micro-organism or virus 

 capable of multiplication in the tissues. 



"Swamp cancer" certainly shows a variation in non- 

 essential characteristics from habronemic granulomata as seen 

 in Southern Australia, but this is possibly due to several 

 factors. In the first place, it is unlikely that "swamp cancer" 

 is due to an invasion of larvae of either H. muscae or H. 

 megastoma. In the second place, horses running in the field, 

 where the natural grasses are not always very nutritious, are 

 likely to react differently from those kept on a highly nutri- 

 tious diet ("hard food"). In the third place, the climatic 

 conditions would have a decided effect on the nature of the 

 reaction to an invasion by a larval Habronema. 



In a previous publication the opinion was expressed that 

 "swamp cancer" is almost certainly a variation of the affection 

 observed in Southern Australia. After a more extensive 

 experience in the examination of specimens, and after certain 

 experimental studies, this opinion is still held. 



In conclusion, it may be said that there is strong pre- 

 sumptive evidence to suggest that "swamp cancer" as observed 

 in the northern parts of Australia is due to the invasion of the 

 tissues by a larval Habronema, and that the species responsible 

 is possibly H. microstoma, in which case it would most probably 

 be introduced into the tissues by Stomoxys calcitrans . 



D. Similar Granulomata as found Outside Australia. 

 1. "Summer Sores." 



This affection was first described, in 1850, by Bouley. 

 Rivolta, in 1868, isolated a worm from the sores, and called it 

 Dermofilaria irritans. Laulanie confirmed this discovery in 

 1884. Since that time man}' - observations on "summer sores" 

 have been published. The literature bearing on the subject 

 has been reviewed by Railliet (1915). 



The affection has been variously named "summer sores," 

 "granular dermatitis," "estival sores," "granular sores," and 

 "esponja." 



A typical lesion shows a granulomatous sore possessing 

 small caseous nodules varying in size from that of a grain of 

 millet to that of a pea. The lesions show variations in char- 

 acter according to the country in which they occur, climate 

 and other conditions, but the presence of the caseous nodules 

 is characteristic. Resistance to treatment, chronicity^ and an 

 accompanying pruritus are also characteristic features of the 

 affection. The parts- most commonly affected are the extrem- 

 ities, but the head and chest, and also the conjunctiva, are 

 frequently the sites of lesions. 



