PREFACE 



A CHANGE of title from "Protozoa and Disease" of four 

 preceding books to "Protists and Disease" has become 

 necessary by reason of my having found that the pathogenic 

 organisms dealt with are not protozoa, but protists allied to 

 Synchytriaceae. In other words, in making comparative 

 study of alien bodies that abound in the lesions of molluscum 

 contagiosum, cancer, and other diseases, we have examined 

 protozoa with great care when we should have given the 

 closest attention to every detail of the life-history of certain 

 vegetable protists, especially Synchytriaceae and some 

 Olpidiaceae. 



But in spite of our having searched in the wrong depart- 

 ment of biology the nature of 'cancer, smallpox, and other 

 human diseases would before now have become plain to 

 all, had there not been some weakness in the foundations 

 of biology. The nature of this weakness is not obscure: 

 it consists in a serious defect in the cell- theory, a defect 

 the bearing of which is shown in chapters of this book, and 

 which may also be briefly outlined here. 



If we bear in mind that the word "nucleus" denotes 



a morphological conception, the cell- theory in its present 



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