S 66 SCIENCE PROGRESS 



point in this direction. One of these relates to the occasional 

 disappearance of tumours. It is well known that tumours, 

 especially those of an embryonic type, sometimes stop grow- 

 ing diminish in size and even disappear under the influence 

 of remedies which can only act through the medium of the 

 general nutrition. Cancer of the breast, for example, has 

 been known to shrink in size and even to disappear after 

 removal of the ovaries. The same thing occasionally happens 

 without special treatment of any kind, perhaps more frequently 

 than is usually believed. At least it is difficult in any other 

 way to account for the single successes of queer remedies 

 which are recorded from time to time, apparently in perfect 

 good faith, and which can never be repeated. In the case of 

 most of these it is not possible to say how or by what means 

 the remedy acts ; but in some it is almost certain that the 

 effect is due to the reagent entering into chemical combina- 

 tion with the living substance of the tumour cells, and thereby 

 altering the reactions that take place in them. Arsenic, for 

 instance, administered internally, sometimes causes certain 

 glandular growths to recede and almost disappear. Then, 

 only too often, after a little while the growth begins to increase 

 in size again, and now the same drug, even in far larger doses, 

 has absolutely no effect. The tumour cells, in other words, 

 have acquired immunity and have become arsenic-fast, just 

 as Ehrlich has shown the spirochaeta can, and for the same 

 reason — the drug has entered into chemical combination with 

 some element in the substance of the growing cell. 



Another of these facts, in many ways even more striking, 

 relates to the production of tumours. It is well known that 

 the continued employment of certain substances, in industry 

 as well as in medicine, is liable to be followed by the growth 

 of certain kinds of tumours. The substances themselves are 

 not the immediate cause of the growth. There is often an 

 interval of years between their administration and the ap- 

 pearance of the tumour. But they initiate such changes in 

 the nutrition of the tissues that when irritation of any kind 

 leads to the rapid production of a large number of young 

 cells, some of these cells stop short of the normal standard 

 of development and form the nucleus from which a tumour 

 bud begins to grow. This has long been known in connection 

 with arsenic. The late Sir Jonathan Hutchinson was the 



