132 



the chronicity of the tumour depends upon a repeated invasion 

 of the tissue by larvae. 



Portions of larvae have been obtained from lesions, and in 

 the better preserved specimens the characteristic spinous tip 

 at the caudal extremity has been observed. It appears, there- 

 fore, that the tumour is a habronemic granuloma. 



Discussion. 



It is remarkable that such a large percentage of horses 

 becomes affected. As far as is known to the present writer 

 there is no previous record of animals becoming affected to 

 anything approaching the extent of 75 per cent. 



Another point of interest is the fact that lesions occur in 

 animals that are not at any time confined to the stable. This 

 is contrary to the usual experience. The animals, however, 

 are not at any time far distant from habitations, so that one 

 would 'expect to find Musca domestica in numbers in their 

 surroundings. 



The fact that the tumours occur only in the one situation 

 is of extreme interest. It is not possible, at present, to 

 determine the exact reason for this. It is possible, however, 

 that the animals may be subject to injuries about the pastern, 

 probably due to some rough, cutting grass. It is remarkable, 

 nevertheless, that wounds in other parts of the body do not 

 develop into habronemic granulomata. 



The occurrence of lesions in one situation only does not 

 suggest that biting flies are in any way responsible. 



The larvae bear the same characteristics as those found in 

 Australia and elsewhere. 



3. "Leeches" and "Bursattee." 



" 'Leeches." — In North America there exists a granuloma- 

 tous affection of equines commonly known as "leeches/ ' 



According to many writers the lesions are to be found on 

 the limbs and those parts of the body which are liable to come 

 in contact with water when animals are standing in swamps. 

 The disease has ' been little investigated, and a considerable 

 confusion has existed as to the pathology of the condition, 

 with the result that it has been described as cancer, and 

 numerous other pathological conditions have been included 

 under this name. 



There seems to be no doubt that the older writers were 

 wrong in classifying this condition as a malignant neoplasm. 

 It is now generally recognized that the condition is a granu- 

 loma, though so little is known of its pathology that many 

 lesions of different etiology are probably still classified 



