436 SIMPLE TUMOURS. 



malignant is not the only growth that is liable to recur, hence 

 the recurrent character of melanosis can only be taken as one 

 fact to prove its malignity. 



I have also seen melanosis in horned cattle of various colours, 

 but more particvilarly in those of a dark brown or black colour, 

 and as a rule early removal has been effectual, and there has 

 been no recurrence. 



A melanotic tumour has all the specialities of malignancy. 

 1st. Its minute structure is not like any of the fully developed 

 natural parts of the body. 2d. It is usually an infiltration ; 

 and this characteristic is much more manifest than in medullary 

 cancer ; although it may appear as separate masses, it will be 

 found, on close examination, that the structures surrounding the 

 tumour are deeply tinged with the pigmentary matter, and that 

 they gradually disappear either by absorption or by being appro- 

 priated as materials for the growth of the malignant disease. 

 Sd. It has a tendency to enlarge, not only by growth, but 

 apparently by multiplying itself in the formation of other 

 tumours around it, or in more remote parts of the body. Ath. 

 Ulceration in melanosis is as constant as in the other malignant 

 tumours. And, lastly, there is scarcely a tissue or an organ 

 that melanosis may not invade. It may, therefore, be safely 

 concluded that " melanotic or melanoid tumours are, with 

 very rare exceptions, sarcomatous tumours, modified by the 

 formation of black pigment in their elemental structures." 

 It may also be mentioned that melanotic tumours in the 

 human being have their favourite seats in or beneath pig- 

 mentary moles. 



Melanosis is, with very rare exceptions, confined to grey 

 horses, and becomes developed as they whiten with age. Its 

 I'avourite seat is on the under surface of the tail, around the 

 anus or vagina, or the perinceum ; more rarely the scrotum, 

 mammary gland, inner surface of thigh, and on the nose or lips. 

 These are merely its outward manifestations ; for on dissection 

 it may be found, either in large masses or as small multiple 

 tumours, in the mesenteric, bronchial, deep inguinal, and lumbar 

 glands, and in the spinal canal. I do not think that there is 

 any part of the body that may not be affected by these tumours ; 

 but I wish to confine myself strictly to those cases that have 

 fallen under my own notice. 



