119 



Possibly, however, these are blood vascular spaces that have 

 been included in the necrotic area. 



The smallest lesion examined was one with a diameter 

 approximately 2 cm. and a depth of about 6 mm. It was 

 raised and had an ulcerated surface. Microscopically there 

 was an extensive invasion of the tissues by eosinophile and 

 neutrophile leucocytes, which were more crowded together in 

 some areas, towards the centre of which typical necrosis had 

 occurred. There were only very few necrotic areas present. 

 The tissues were oedematous and haemorrhagic. The 

 epidermis was in parts oedematous, and invaded by leucocytes. 

 This change had led to ulceration with the formation of a 

 vascular granulation tissue. Towards the edge of the lesion 

 the epidermis showed considerable hypertrophic changes, the 

 epithelium dipping deeply into the subcutaneous tissues, and 

 showing numerous small processes. This hypertrophic change 

 in the epithelium indicates an irritation of some standing. 

 The necrotic areas were sometimes ill-defined and diffuse, and 

 there was no attempt at encapsulation. Multinucleated cells 

 were seen in several parts of the section. 



The whole lesion was examined in serial section and no 

 larvae were discovered. The lesion, although a very small 

 one, was probably of several weeks' standing, and not as 

 early as might be assumed from its size. A consideration of 

 the hypertrophic changes in the epithelium, which must have 

 been of several weeks' duration, led to this conclusion. 



It may be mentioned here that there is a granulomatous 

 condition affecting horses in the Solomon Islands known under 

 the name of "swamp cancer." This condition is discussed else- 

 where, and must not be .confused with the "swamp cancer" of 

 Northern Australia. 



Discussion. 



There is a great similarity between the macroscopic and 

 microscopic pathology of "swamp cancer" and habronemic 

 granuloma as observed in Southern Australia. 



The condition is undoubtedly a granuloma, and is due to 

 a reaction on the part of the tissues to an invasion by some 

 organism. It belongs to that type of reaction most commonly 

 seen in animal tissues that have become invaded by some larval 

 or adult verminous parasite. The reaction is so similar to that 

 seen in some habronemic granulomata as to suggest that the 

 condition is due to a similar cause. No larvae have been found 

 in the tissues, but this is not proof that they have not been 

 there at some time, and that the tumour is not the result of 

 the invasion. At the same time there is no proof that larvae 

 are responsible for the reaction. 



