MALIGNANT TUMOURS IN ANIMALS. 



585 



frequency of mammary tumours. We have studied nineteen, one of 

 which was obtained from a mare ; the others being of canine origin. 



The tumour from the mare, and eleven of the tumours removed 

 from bitches, showed the histological appearances of epitheliomata. 

 They were composed according to the classical schema of a stroma 

 surrounding alveolar cavities. In these cavities the epitheliomatous 

 cells were generally arranged around the margin, producing acini, in 

 the centres of which was sometimes found a clear substance exuded 

 undoubtedly by the newly formed cells (Fig. 85) ; but most frequently 

 (Fig. 86) degenerating cells without nuclei, which were stained a dirty 

 yellow by picrocarmine. At places the new growth deviated from the 

 original type and showed irregularly arranged cells contained within 

 alveolar cavities, or grouped together in large masses. In some cases 

 the stroma predominated, displacing the new cells and producing the 

 appearance of scirrhous cancer. 



Among other tumours developed in the mammary glands we first 





Fig. 87. — Fusiform-celled sarcoma from the mammary gland of the bitch. 



mention two fusiform-celled sarcomata (Fig. 87). The cells contained 

 large nuclei provided with clearly marked nucleoli ; at certain points 

 degenerating cells could be seen. 



In three cases we found a form of sarcoma with rounded or oval 

 cells massed together or scattered through a chondroid, hyahne, or 

 fibrillated substance, showing at several points true chondroplasts pro- 

 vided with cartilaginous cells (Fig. 88). 



In other cases the development of the growth had led to formation 

 of a tissue resembling bone ; of this we saw two examples. In one 

 the tumour was formed of granular blind sacs ahernating with hyahne 

 cartilage and osteoid growths ; osteoplasts and canaliculi could even 

 be detected, though the latter were less numerous and less well defined 

 than normal. - ' 



