SOFT CANCER. 423 



hence their liability to bleed when the tumour ulcerates, or 

 when wounded accidentally ; and it is due to this that the name 

 fungus-hsematodes has been applied. 



Medullary cancer may arise from an accidental injury, such 

 as a blow or wound. In the case of cancer of the side of thorax 

 and abdomen (page 414), the tumour arose in the cicatrix of an 

 old wound ; the tumour had been present for several years, and 

 gradually increased in size, until it became unsightly, and inter- 

 fered with the application of the saddle-girths. 



EPITHELIAL CANCER. 



Epithelial cancerous tumours, also known as epithelioma 

 or cancroid, consist of a fibrous stroma, in which papillse and 

 epithelium are found greatly multiplied and enlarged. The cells, 

 when microscopically examined, are found to be numerous, flat, 

 round, oval, or elongated, containing a simple nucleus ; and other 

 cells containing large nuclei, which appear as if in process of 

 development into cells. They differ but little from the natural 

 epithelial cells of the part ; and as the minute structure of this 

 form deviates least of all the cancers from the natural structures 

 upon which it grows, so its course and history exhibit but little 

 malignancy. 



Its chief site is the skin and mucous membranes, but particu- 

 larly at the junction of the two ; as the mouth of mucous orifices, 

 the vulva, anus, eyelids, and edges of the mouth. It is a very 

 rare form in the lower animals ; arises from some previous local 

 disease or injury ; and is seen more frequently in dogs than in 

 the other domesticated animals. — (Fig. 99.) 



MELANOSIS, OR BLACK SARCOMA. 



Melanosis, described in the last edition of this work as Black 

 Cancer, is found, upon further investigation, to belong to that 

 class of tumours now known as the sarcomata, or tumours con- 

 sisting of embryonic connective tissue, of which several forms 

 are described, namely, fibro-plastic, fibro-nucleated, recurrent- 

 fibroid, and myeloid tumours. — (See Paget, Green, &c.) 



In structure the sarcoma consists of connective tissue, which 

 retains its embryonic characters and cells, which constitute nearly 

 the whole of the growth, presenting three principal varieties — the 

 round, the fusiform, and the myeloid cells. The round cells are 

 those generally found in the melanosis of the lower animals, and 



