S8o CLINICAL VETERINARY MEDICINE AND SURGERY. 



nine to ten years ; five at eleven to twelve years ; two at fourteen 

 years ; and one at twenty years. In the horse the age varies between 

 seven and fifteen years. The nature of the congenital tumours 

 described by some authors has not been established by sufficiently 

 exact microscopic examination to justify us in admitting their 

 existence. 



Primary cancers generally appear on the surface of glandular 

 organs, or in external parts exposed to mechanical irritation. It has 

 been suggested that in the horse friction of the harness is sufficient to 

 produce cancer. In reality these growths are chronic inflammatory 

 indurations, sometimes exhibiting the appearance of fibromata, or are 

 parasitic lesions due to the presence of bothryomyces. Mere 

 mechanical injury is not sufficient to produce the growth of tumours; 

 observation tends to establish this point, and experiments also point in 

 the same direction. We mechanically irritated the mammary gland 

 in several old eczematous bitches ; every day, or every two days the 

 glands were compressed and bruised by means of strong w'ooden for- 

 ceps ; although the experiments were continued for months, we never 

 succeeded in producing new growths, and only in two cases did an 

 abscess form. 



Mechanical injury, therefore, only plays a secondary part. The 

 same is true of the hygienic conditions under which animals exist. 

 Contrary to the statements of some authors, we believe that it is 

 impossible to render animals cancerous by submitting them to 

 special life conditions. But it seems, according to Leblanc's state- 

 ment, that animals restricted to meat diet and chained or shut up 

 are more often affected with cancerous lesions than others. 



Among predisposing causes it is still usual to mention gout. 

 M. Trasbot strongly insists on the part played by this diathesis. 

 According to him, dogs, and even horses, suffering from cancer have 

 almost always previously shown eczematous eruptions. 



At the present time the tendency is to consider cancer as a 

 parasitic affection, and cases have been described in man which 

 appear to establish this contagious character. We have noted 

 nothing similar in animals. All the attempts we have made to 

 transmit new growths from man to the dog, from dog to dog, or from 

 the dog to the rabbit or fowl, have uniformly failed ; nor were we 

 more successful in attempting to graft fragments of their own 

 tumours on healthy parts of cancerous dogs. On two occasions we 

 seemed at first to have obtained a positive result ; but in one of 

 these cases the secondary tumour had none of the histological cha- 

 racters of the primary ; and, in the other, the lesions, though ofi'ering 



