117 



the proboscis of Musca domestica when that fly comes to feed 

 on moist surfaces. The escape of the larvae from the proboscis 

 appears to depend upon the rupture of certain structures in 

 the proboscis. This rupture appears to depend directly upon 

 the number of larvae present and their activity. Unless 

 conditions are such as to allow of the development of a large 

 number of larvae in the fly, and the temperature is high 

 enough to produce marked activity in the larvae, then it 

 would appear that the escape of larvae from the proboscis is 

 not very likely to occur. Experimental observations have 

 shown that the escape of larvae from the proboscis is not 

 of frequent occurrence. (3) All animals do not appear to be 

 susceptible. (4) It seems possible that certain strains or 

 varieties of the same species are more likely to produce lesions 

 than others. 



In each granuloma examined there have been a large 

 number of larvae or necrotic areas present. This indicates that 

 there is usually a massive infection at one point. Super- 

 infection has not been found to be of common occurrence. 

 Only in one tumour examined was this suggested by the fact 

 that larvae showing marked retrogressive changes were present 

 along with others showing very early retrogressive changes. 

 Massive infection at one point, therefore, does occur, and is 

 probably explained by the fact that the larger the number of 

 larvae present in the proboscis of a fly the more likelihood of 

 rupture of the proboscis and the escape of the larvae. 



! Tumours on the glans penis have always been found at 

 the urethral orifice. This suggests that flies are attracted to 

 the moisture about the meatus, and that the larvae after 

 escaping from the proboscis make their way through the 

 mucous membrane of the urethra, and not through the modi- 

 fied skin covering the glans penis. This is supported also by 

 the fact that the necrotic foci are found close to or involving the 

 urethral mucosa while they may be relatively a considerable 

 distance from the external surface. 



C. Granulomata as found in Northern Australia. 



General. — A granulomatous affection of horses, commonly 

 known as "swamp cancer," and described by Lewis (1914) 

 under the name of equine granuloma, is found in the northern 

 or tropical portions of Australia. The condition has been 

 thoroughly described by Lewis, who studied it in the field, 

 and also conducted some experimental work in an attempt to 

 artificially produce the disease. 



The present writer was impressed with the great similarity 

 between this condition and the granulomata observed in 

 Southern Australia. On request, specimens of "swamp 



