JoLY — Radio- Ther'apy : its Scientific Basis and its Teaching. 509 



which might be held responsible foi- the increase of cancer. Many 

 accustomed articles of diet may, doubtless, contribute in some degree 

 towards increased cell mitosis and yet be quite harmless under the conditions 

 of consumption. As already stated, it is known that alkaline solutions of 

 lactose and glucose possess the parallel qualities required for affecting the 

 photo-sensitive films. I have not obtained this action on the ordinary dry 

 plate, nor got any latent image with ordinary sugar in alkaline solution. 

 Milk, however, gives a faint effect, and tliis may bo due to lactose, Sugar 

 is an article of diet, the consumption of which has increased in modern 

 times, and the evidence for its sensitizing activity— eitlier directly or 

 indirectly — should not be lost sight of as possibly concerned in the cancer 

 problem. 



But a far more suspicious substance is found in tannin. This substance 

 enters, as all know, largely into the composition of teas of all varieties to the 

 extent of, usually, 11 to 26 per cent. ; and 60 to 80 per cent, of this is 

 obtained in the normal extract. Tea, as an article of diet, has replaced all 

 other beverages in the light meals of the day. This especially applies to the 

 better-off classes. In former years this beverage was only taken at " tea- 

 time." The cancer statistics when compared with the statistics for the 

 consumption of tea in tliis country show features in common. Both 

 curves rapidly rise for several decades preceding tlie last, and within recent 

 years show a somewhat less rate of increase.' 



As regards tlie consumption of tannin in other countries, it is to be 

 remarked that this substance enters into coffee to the extent of about 22 per 

 cent., and is present in red wines. Obviously without statistics both as to 

 tlie consumption of tannin-containing beverages and of the prevalence of 

 cancer we cannot discuss the geographical evidence. It is stated that in 

 China cancer has long been a prevalent disease. 



Tannin or gallotannic acid is itself a photographic sensitizer, and has long 

 been known as such. It absorbs the halogens.^ It is the parent substance of 

 a complicated and only partially studied group of substances in which the 

 reducing properties required for development and sensitization seem to prevail. 

 Thus gallic acid, a derivative whicli does not coagulate albumen, and is said 

 to be absorbed in the body by administration of tannic acid, is a developer 

 and sensitizer. Another derivative is the powerful developer pyrogallic acid, 

 which along with gallic acid is st;ated by some writers to be excreted by the 

 kidneys. As transported in the circulatory system tliese substances must, of 



' Compare figures given for tea-consumption in Thorpe's " Diet, of Applied Chemistry," article 

 " Tea," with the Cancer Tables in Burns's " Vital Statistics Explained," Constable, London, 1914. 

 2 Meldola, loc. eit, p. 98. . - 



