SMALLPOX, SYPHILIS, CANCER, ETC. 211 



made in the last 30 years respecting the pathology of cancer : 

 what used to be called an alveolar sarcoma is now called a 

 perithelioma. The insistance is on histogenesis ; a slight 

 movement on a road well made by Virchow. And what a 

 good road it has been and will continue to be ; helping us 

 to decide points in diagnosis and prognosis, and affording 

 reliable indications as to treatment ; helping us to trace the 

 primary seat of growth when the tumour that is the first to 

 show itself clinically is found to be composed of tissue foreign 

 to that in which it occurs ! Certain types of cell-forms and 

 of structure in tumours we know to be associated with 

 corresponding degrees of malignancy. 



Beyond Virchow' s is another road, at present a mere 

 track in places. The old road must be patiently traversed 

 before the new one can be reached. Unless this new road 

 is followed patiently and thoughtfully, and all the menacing 

 objects it brings into view are scrutinised critically and 

 tested by experiments planned on natural lines, the causes 

 of the diseases dealt with in this book and of many others 

 must remain unappreciated. 



