CHAPTER V 



UNIPOTENTIALITY, PLURIPOTENTIALITY, AND TOTIPOTENTIALITY 

 OF CELLS : A NOTE UPON THE CLASSIFICATION OF TUMOUES 1 



(1907) 



A few years ago I published a paper upon the classification of 

 tumours based upon the embryogeny of the different tissues. 2 

 That classification, I confess, was somewhat elaborate in appear- 

 ance, although simple in principle, based upon the fact that each 

 primitive cell layer gives rise to tissues of two orders, to denote 

 which I was compelled to introduce a new set of terms. I did not 

 like to do this, nor was it my idea that these terms should in any 

 way attempt to replace in general practice those honoured by 

 long use. Nevertheless, mere length of use has brought about 

 such vagueness in the employment of the latter that for scientific 

 and exact purpose they have very largely lost their primitive 

 value. These terms notwithstanding, it is some satisfaction to 

 see that that classification is coming to be accepted by writers 

 of systemic works on pathology as the most rational so far pro- 

 posed. To-day I wish to call attention to what I regard as a 

 further advance in our conception of the relationship of the 

 different forms of tumour which permits us to make in some 

 respects a still more exact classification. 



It may be remembered that in my older classification I divided 

 neoplasms into two great groups of the teratomas (the tumours 

 due to the development within the body of one individual of 

 tissues and parts belonging to another individual) and the 



1 A paper read before the Pathological Section of the Canadian Medical 

 Association, Montreal, September 1907. 



2 Journal of Pathology and Bacteriology, iv., 1902, 243 [pp. 305 et seq. of 

 this volume]. 



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