78 PROTOZOA AND DISEASE 



the cells of which the body or part of it is built up, as was established 

 by Virchow in 1847. As applied to cancer, the truth of the main 

 part of Virchow's teaching is incontestable ; the bloodvessels of 

 these tumours can be injected from the main artery of the body, 

 showing that they and the cells that constitute them are part of the 

 general vascular system. In primary 1 epithelial cancers many 

 cellular elements 2 besides those of the bloodvessels can also be 

 traced to be in structural continuity with the adjacent normal 

 tissues, and the following pages will show that the same continuity 

 of structure exists in some connective-tissue cancers, not only in 

 the primary, but in all the lesions. 3 



1 Virchow and his followers regard all the constituent cells of 

 cancer as lineal descendants of cells which once formed part of the 

 body of the animal in which the tumour grew. The accuracy of 

 Vichow's description of the histological structure of cancer and 

 sarcoma has been proved again and again ; the only question with 

 regard to them is one of interpretation.' 4 



In many cancers the structure of the tissue is so changed, and 

 the forms of the cells, their structure and arrangement, are so varied, 

 as to give a bewildering prospect when the tissue is seen in sections 

 under the microscope. Some authors for instance, Arnold, 5 von 

 Hansemann, and others have described many varieties of nuclear 



1 By a 'primary' tumour is meant the original tumour; if more than one 

 tumour is present it is possible that two or more of them appeared at the same 

 time. In such a case there would be more than one primary tumour. 



2 That is, the structures readily recognised to be cells under a medium power 

 of the microscope /.., ordinary cells, as distinguished from bacteria. 



3 The term 'lesion' or ' damaged part' appears to the writer to be preferable 

 to such names as ' morbid growths,' etc., which involve ideas that require recon- 

 sideration. 



4 Virchow's original view of the cells of cancer was that they all belonged to the 

 connective tissue : this error was corrected by Waldeyer. The passage quoted is 

 from the writer's book ' Morbid Growths and Sporozoa,' published in 1893. 

 I r urther quotations from this work will be made, but, for the sake of simplicity, 

 references will not be made to that work save when necessary. 



5 A short notice of work done up to that date appears in the Transactions of 

 the Pathological Society, 1894, p. 245, as an introduction to an article by myself 

 on cell-forms in a myxosarcoma. 



