510 Scientific Proceedings^ Royal Dublin Society. 



course, acquire neutral or faintly alkaline characters. Other substances 

 whicli possess tlie requisite reducing properties, and are constituents of the- 

 complex tannins, are pyrocatechol and hydroquiuone. 



Thein (or cafPein) does not appear to exert more than a very feeble effect 

 on the film, even when in a state of saturated solution, either neutral or 

 distinctly alkaline. 



If the increased prevalence of cancer is wholly or in part traceable to the 

 increased consumption of tannin, we must regard the derivatives of i\\\&- 

 substance as predisposing tlie cells throughout the body to the incidence of 

 the disease. The appearance of the disease at any particular point in the 

 body is probably determined by local stimulus of cancerous mitosis. The^ 

 view suggested is that a general instability or irritability is promoted 

 throughout the body cells by this substance tannin ; or rather, by the 

 derivative or derivatives of it which are absorbed in the body ; the effects 

 being mainly due to the reducing or halogen-absorbing properties. A state 

 is at length reached after long and excessive absorption of tlie injurious 

 substance in which local causes are competent to precipitate the pathological 

 mitosis and cell proliferation. These causes are various. It may be a local 

 chemical stimulus, as by the application of a powerful sensitizer such as nico- 

 tine, or possibly, " nut-gall ointment." Other local causes, as has often been 

 suggested, may be the increased mitotic activity prevailing in the organs of 

 generation. Here there is already a local approximation to the conditions 

 induced by increased electro-negative ionisation. Mechanical stimuli are 

 probably responsible for the sweep cancer, etc. 



The frequent recurrence of cancer after its local extirpation or destruction 

 follows as a matter of course according to the present views. For, even apart 

 from metastatic spread of the disease, the local cure is likely to be only tem- 

 porary' if the patient continues to absorb tlie sensitizing agent into his system, 

 or, possibly, has already permanently affected his tissues by its use. Where 

 so much is involved, should not the physician consider the advisability of the 

 denial to the patient of tannin-containing beverages ? 



The effect of tannin as an influence on mitosis is probably responsible 

 for the phenomenon of " vegetable cancers " or galls on trees and shrubs. 

 Galls may contain up to 75 per cent, of tannin. These growths originate 

 under the stimulus of irritation by some insect. Pfeffer, Sachs, and others 

 have recognized that tannin in plants is abundant in places where growth is 

 specially active ; such as growing points, pathological growths, and places 

 where the protoplasm is specially irritable.' We must remember that when 



' Haas and HiU : " Chemistry of Plant Products." (London : Longmans, Green, & Co., 1913.) 



