APPENDIX A 271 



applied, always produce malignancy. With regard to 

 radium, I understand that Lazarus-Barlow claims to have 

 produced by it a " pre-cancerous " growth in rats and 

 rabbits. These altered tissues were only slightly invasive, 

 and when the radium action was stopped they resumed 

 their normal character. It is held by some that this 

 proves the necessity of a second factor which may be 

 parasitic, but the strictly logical view is simply that the 

 organism recovered, i.e. that the normal tissue inhibitions 

 were restored, and that the altered tissues resumed their 

 ancient functions. Since we know that, even in obvious 

 cancer, attempts of the organism to cure it succeed for 

 long periods, it is illegitimate to infer that an artificially 

 produced morbid state of possible malignancy in a healthy 

 subject may not revert to a normal condition when the 

 disturbing influence is removed. 



With regard to the difference between benign and 

 malignant tumours, which some think are such as to divide 

 them entirely into classes of wholly different causation, 

 it may be said that much late work does not support this 

 view. The fact that so many benign growths at last be- 

 come malignant, and that in others the dividing line is 

 so obscure that the histologist and pathologist are doubtful 

 as to their character, obviously suggests that a further 

 want of inhibition or the increase of some undue stimula- 

 tion may end in malignancy. A few authorities argue 

 that even benign tumours are parasitic in their origin. 

 All that is necessary to say of this is that such a theory 

 of causation appears superfluous. 



Perhaps the best defence of the parasitic theory is 

 that of D'Este Emery {Tumours, 1916). It is well 

 argued, and likely to convince those who arc already 

 inclined to take the view supported. Many of the 



