122 PROTOZOA AND DISEASE 



In the typical rapidly-growing periosteal sarcomata several 

 parasites are to be seen in every microscopic field, but in the typical 

 central sarcoma, on the other hand, the parasitic inclusions are 

 often very few in number; two or more sections may sometimes be 

 carefully examined before one is found. When they are found their 

 characters are very definite, and make it easy to recognise them at 

 once. They are usually seen within one of the giant-cells (myelo- 

 plaxes) as relatively large hyaline bodies surrounded by a space, 

 which is often lined by a doubly refracting capsule. 



The cell-inclusions such as these in this periosteal sarcoma 

 that first arrested my attention in sarcoma I described as protozoa 

 in I8Q3. 1 They were subsequently described as blastomycetes by 

 Sanfelice and Roncali, 2 whose work attracted close attention to 

 the pathogenic blastomycetes, and, together with cases of blasto- 

 mycetic dermatitis described by Drs. Gilchrist and Rixford 3 and 

 others, has resulted in showing how closely some of the blastomycetes 

 resemble certain protozoa, especially the coccidia. It is only when 

 the cell-inclusions and other bodies foreign to the tissues are studied 

 in a series of sarcomas of different kinds, and especially in such a 

 one as the alveolar sarcoma of the breast described above, that the 

 series of forms and the relationship between the tissue-cells and the 

 foreign elements is found to be such that the bodies in question can 

 belong only to the protozoa ; so varied are the forms and so intimate 

 the parasitic adaptation. 



One feature of great importance is exhibited by the periosteal 

 sarcoma : this is that the secondary growths have the same 

 characters as the primary growths, both as regards the tissue-cells 

 in these secondary growths and the parasitic bodies. This is in 

 contrast with what obtained in the alveolar sarcoma of the breast. 

 In the latter the tumours were the ordinary connective tissue 

 reacting to an invasion of parasites, and secondary growths might 

 arise in any part of the body without actual transference of the 



1 Brit. Med.Journ., January 21, 1893. 



2 Sanfelice and Roncali, Cent, fur Bakt., 1895, p. 625. 



3 Gilchrist and Rixford, Johns Hopkins Hospital Reports, 1896, vol. i. 



