THE HABIT OF GROWTH 59 



into columnar epithelium, and vice versa, as again to explain 

 the neoplasias or true tumours, 1 here calling attention to the 

 partial antagonism between functional activities of the cells, 

 in which the food-stuffs absorbed are utilized in the production 

 of energy in the exercise of function, and the vegetative activities, 

 in which the food-stuffs absorbed are employed in the building 

 up of increased cell substance and utilized for growth and pro- 

 liferation. The time at my disposal forbids that I should enter 

 at length into the data supporting the " habit of growth " theory 

 of neoplasia, but as bearing upon cell inheritance of acquired 

 properties I cannot forbear calling attention to a form of cancer 

 of which I have come across at least two well-marked examples, 

 and of which there are several other cases by Van Hansemann 

 and others on record. I refer to primary squamous epithelioma 

 of the gall-bladder. 2 Normally there is no squamous epithelium, 

 but only columnar epithelium in the gall-bladder. There is no 

 squamous epithelium anywhere in the neighbourhood. But it 

 is a familiar fact that 90 per cent or over of cases of cancer of 

 the gall-bladder are associated with the presence of gall-stones. 

 It has also been noted by several observers that the continuous 

 irritation set up by the presence of gall-stones leads to the meta- 

 plastic conversion of areas or plaques of the columnar-celled 

 mucosa, more particularly of the fundus of the gall-bladder, into 

 a stratified squamous epithelium. And here is the interesting 

 point : we encounter cancers of the gall-bladder, not of the pure 

 adenomatous or cylindrical-celled type, but containing definitely 

 epitheliomatous areas. In other words, in these cases the meta- 

 plastic squamous epithelium, originating from a columnar-celled 

 mucosa, has had its new character so firmly impressed upon it 

 that when it is stimulated to new growth it does not revert to 

 an adeno-carcinomatous type, but retains the impressed varia- 

 tion and gives rise to epitheliomatous squamous-celled down- 

 growths : an acquired variation becomes hereditarily transmis- 

 sible among these cells, just as must be the case when the 

 production of antibodies lasts for months and years. 



1 See the address on " The Causation of Cancerous and other New Growths " 

 reprinted as Chapter II. of Part III. of this volume. 



a For the different forms of new growth, their classification and histogenesis, 

 see the address on " The Classification of Tumours " in Part III. of this volume. 



