ACCESSORY FOOD BODIES 115 



extract. To quote one of the experiments: Six 

 flasks, A to F, were taken and filled with 100 c.c. 

 of normal culture solution. To the first nothing 

 was added, but to the others decreasing amounts of 

 Silver nitrate extract. The quantities used and 

 the results obtained on incubation are shown in the 

 following table : 



In other words, when the Silver nitrate extract was 

 added to the amazingly small extent of i part in 

 15,000,000 an appreciable result was obtained. 



Tests were made with a large number of other 

 organic substances to see whether the scum would 

 be formed in their presence. The result in every 

 case was negative until 100 parts per 1,000,000 were 

 added. Even then the characteristic scum was not ob- 

 tained, as the whole liquid was found to turn cloudy. 



Further comparative tests were made with the 

 accessory food bodies that had been found to give 

 results on animals. When they were derived from 

 germinated wheat, dry wheat, peas, or yeast, the 



