CHAPTER III 



ON THE CLASSIFICATION OF TUMOURS 1 

 (1902) 



ONCE it was established by histological studies that the different 

 forms of neoplasms arise from different tissues, it became possible 

 to group tumours according to their origin. Once again, when, 

 through the observations of the embryologists, it was recognized 

 that the tissues could be grouped according to their origin from 

 the primitive cell layers, it became possible to group tumours 

 in the same way. This was done more especially by Waldeyer, 

 and we obtained thus a classification of tumours into those of 

 mesoblastic origin and those of epiblaslic and liypoblastic derivation, 

 the tumours derived from the two latter cell layers being grouped 

 together, for it was soon found that they were of the same general 

 type. 



Here was a broad and very important generalization, and, 

 what is more, in the then stage of histological and embryological 

 knowledge, it appeared not only to be founded on a sure and 

 scientific basis, but to fulfil to the fullest the needs of the worker. 

 For it appeared to separate two sharply differentiated orders of 

 tumours those of connective tissue origin and connective tissue 

 type from those of epithelial and glandular origin and epithelial 

 and glandular type. So that for long years this distinction 

 remained dominant ; even to-day, in at least one text-book 

 published during the last twelve months, that by Dr. Nicholas 

 Senn, this is given as the acceptable classification. 



It is, however, scarcely necessary to say that, with increasing 



1 The main body of this paper was contributed as an address to the Toronto 

 Pathological Society, January 4, 1902. Reprinted from the Journal of Patho- 

 logy and Bacteriology, Edinburgh, June 1902. 



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