ABNORMAL GROWTH. TUMOURS 271 



the growth of its epithelium typical. Naturally, one would 

 not expect the connective tissue to exert its power for very 

 long in vitro, as it itself is removed from the normal growth 

 influences of the body. Prolonged growth in vitro could 

 never be accompanied by re-differentiation, but only to 

 atypical cells with characters harmonious with the artificial 

 environment ; but in time some form of debased gamete 

 would presumably be produced. 



What we may then conclude is that epithelium in the 

 living body cannot grow typically in amount and character 

 unless it is in touch with the supporting connective tissue 

 which is its normal immediate " internal " environment, 

 and from which it receives certain normal growth influences. 

 And this conclusion is one we could arrive at from what 

 we see in the healing of a granulating wound, for the 

 epithelium will not grow across bare muscle, bone, or cartilage, 

 or bridge a space ; it requires to advance in touch with 

 new connective tissue in the form of healthy granulations. 

 The skin graft exhibits the same phenomenon, for it will 

 only " take " if placed on or in its proper immediate 

 environment, healthy granulation tissue. 



Let us take the case of an epithelioma of the lip or the 

 tongue, developing at the site of some chronic irritation. 

 Regarding the onset of malignancy several possibilities 

 suggest themselves. (1) That the marginal epithelium comes 

 to grow out of touch with its restraining connective tissue, 

 so that the growing edge gradually escapes from control. 

 (2) The connective tissue granulations may become so 

 unhealthy owing to the continued action of the irritant 

 that as an immediate environment they cease to have a 

 proper restraining influence. (3) In the absence of granu- 

 lations of any kind the epithelium may insist in growing 

 without any restraining influence. (4) Through advancing 

 age, or other general cause, affecting the body as a whole, 

 the controlling power of the connective tissue is weakened 

 and breaks down. 



The absence of granulations in ulcers which become 

 malignant is a common phenomenon, and the long processes 

 of malignant cells which burrow down into the base of an 

 epithelioma, and the curling cell-nests as observed in such 

 a tumour in the lip, strongly suggest that in the absence 



