TUMOURS AND CANCERS. 239 
whilst they are yet alive, on a suitable stage, these cells 
have been found to exhibit amoeboid movements and 
change of shape. When such cells die they assume a 
rounded form, in the same way that a dead leucocyte 
becomes transformed from an irregular shapeless mass 
of active protoplasm to a definite rounded cell. 
To put the matter in a clear form, a sarcoma is pro- 
bably the scene of action of a violent and prolonged 
Fic. 12t.—The microscopic appearance of a round-celled 
Sarcoma. 
conflict between irritant micro-organisms and leucocytes. 
I say probably, because, as has been already remarked, 
bacteriologists have not yet succeeded in isolating a special 
bacterium for sarcomata in general ; that such agents 
will soon be discovered is in the highest degree probable, 
because in recent years each increase in the list of infec- 
tive granulomata is made at the expense of sarcomata. 
The structure, mode of growth, infective properties, and 
