198 



Scientific Proceedings (114). 



candles without losing their growth-inducing properties. It was 

 thought not unlikely that the growth-stimulating effect of these 

 bacterial extracts might be due to substances belonging to the 

 class of the so-called vitamines. To test this assumption, similar 

 extracts were prepared from yeast cells which are known to be 

 rich in growth accessory substances. These extracts, even in 

 minute amounts, were found capable of promoting growth. Ex- 

 traction of the growth accessory substances from another source, 

 namely, green vegetables, was tried; extracts of fresh tomatoes, 

 green peas and string beans were found remarkably active in 

 stimulating growth. These active yeast or vegetable extracts 

 when added to broth greatly accelerate growth of organisms such 

 as Bacillus influenzal and pneumococci, so that within five hours 

 abundant growth is evident. In the case of pneumococcus, a 

 seeding too minute to initiate growth in plain broth alone will 

 amply suffice to induce abundant growth in the same medium if 

 a small amount of extract containing these growth accessory 

 substances is added. In the case of Bacillus influenzal, when 

 seeded from blood media, luxuriant growth occurs in plain broth 

 containing yeast extract, while no growth takes place in the same 

 broth without the addition of extract. The presence of these 

 growth accessory substances in extracts diluted 1 : 1,000 suffices 

 to stimulate growth under these conditions. However, for reasons 

 to be discussed later, continued cultivation fails in broth con- 

 taining only yeast or vegetable extracts. 



While the nature of these growth accessory substances is not 

 known, they are presumably analogous to the so-called vitamines. 

 It has been found that they resist boiling for at least ten minutes, 

 that they are destroyed by autoclaving, that they are extractable 

 from fresh vegetables and from growing bacterial and yeast cells, 

 that they are water soluble, that they pass a Berkefeld filter, and 

 that extracts of these substances contain but little nitrogen — 

 about 0.1 16 per cent. 



In the application of this principle to bacterial nutrition, 

 particular attention has been given thus far to the nutritional 

 requirements of Bacillus influenzas, since this organism belongs to 

 a peculiar group of bacteria which heretofore have been considered 

 obligate hemophiles. 



