237 



Some Accessory Factors in Plant Growth and Nutrition. 



By W. B. Bottomley, M.A., Professor of Botany, University of London, 



King's College. 



(Communicated by Prof. F. W. Oliver, F.R.S. Received May 29— Read 



June 18, 1914.) 



Recent research has demonstrated the importance of the presence of 

 minute amounts of certain substances as accessory factors in normal 

 dietaries of man and animals. The most striking examples of the 

 influence of these substances are seen in their curative effect on the diseases 

 of beri-beri and scurvy, and their stimulative effect on the growth of young 

 animals. 



Beri-beri is caused by the deficiency in a diet of polished rice of a 

 nitrogenous substance, small amounts of which are essential for the 

 metabolism of the nervous system. The curative substance is found in 

 rice husks, barley, wheat, lentils, yeast, egg-yolk, milk, etc., and is pre- 

 cipitated from an aqueous solution of an alcoholic extract of these bodies 

 by phosphotungstic acid. It is effective in very minute amounts, an 

 addition to the diet of - 02 grm. of the active fraction of the extract 

 curing polyneuritis (beri-beri) in pigeons. 



Scurvy also is caused by a diet adequate as regards proteins, carbohydrates 

 and fats, but deficient in some constituent, small amounts of which are 

 essential. This anti-scorbutic substance is found in lime-juice, fresh 

 vegetables and fruits, and, like the curative substance of beri-beri, is 

 precipitated by phosphotungstic acid. 



The special importance of small amounts of substances of unknown com- 

 position in the metabolism of growing animals has been demonstrated by the 

 recent researches of Osborne and Mendel* and Hopkins.f These investiga- 

 tions have shown that young rats, fed on a diet consisting cf a mixture 

 of pure proteins, carbohydrates, fats, and inorganic salts, failed to grow, 

 but on the addition of a very small amount of certain substances obtained 

 from milk growth was normal. Hopkins found that the fraction obtained 

 from a phosphotungstic acid precipitation of proteid-free milk contained 

 the active substance and gave excellent growth results. As a result of 

 his experiments he states that " the presence of minute traces of certain 



* Osborne and Mendel, Carnegie Institution Publication No. 156, Parts I and II, 

 1911. 



t F. G. Hopkins, ' Journ. Physiol.,' vol. 44 (1912). 



VOL. LXXXVIII. — B. T 



