AN ALVEOLAR SARCOMA 105 



apparently structureless bodies to degeneration. And I repeat, with 

 regard to the various structures that I have described as protozoa 

 in the foregoing account of this tumour of the breast, that there is 

 but one interpretation of them which completely explains them and, 

 at the same time, the whole of the phenomena of the tumour in 

 which they occur, and this interpretation is the one I expressed in 

 1895 viz., that the bodies are protozoa. Further, a close study of 

 the relation of these protozoa to the tissue in which they lie shows 

 that this typical alveolar sarcoma is an infection of connective tissue 

 and muscle cells by this protozoon, which is of amoeboid character ; 

 also that the structural alveolar character of this particular sarcoma 

 is due to the fact that there is no defence either on the part of the 

 tissues or leucocytes against the protozoa, no proliferation of 

 connective-tissue cells, and no phagocytosis by macrophages or by 

 leucocytes ; the tumour is alveolar because the connective-tissue cells 

 of each capillary area swell both by the distending presence of the 

 parasites within them and by the so-called * hypertrophy ' that para- 

 sitic protozoa cause in the cells which they infest. 



