Studies on the Life History of Protozoa. 429 



action of the pancreas extract. Fig. 8 represents an individual 

 twenty-four hours after treatment, i. e., after change from pancreas 

 extract into hav infusion.^ The characteristic dense structure is 

 distinctly shown, but in the center there is unmistakable evidence 

 of the normal condition. Figs. 9 and 10 represent two indi- 

 viduals forty-eight hours after treatment with the pancreas extract. 

 In the former, the characteristic dense structure is still visible at 

 the two ends, but the center is clearing. In the latter, new gastric 

 vacuoles have appeared in the endoplasm, the animal being well 

 on toward recovery when killed. 



c. Extract of Sheep's Brain. This was made in the same way 

 as the other meat extracts, and the animals were similarly treated 

 with it. It was not efficient as a permanent stimulant, and was 

 discarded in subsequent treatment. 



d. Extract of Mutton. '' Mutton Broth.'' This extract was also 

 tried in the summer (July 20 and 23), but in no case was it 

 successful, the organisms invariably dying within 24 hours. 



e. Lecithin. A trace of pure lecithin was put into the regular 

 hay infusion during the week of August 20. The organisms were 

 apparently not injured by the change, but did not live more than 

 48 hours after the treatment. 



/. Pineapple Extract. With the view of ascertaining if some 

 of the vegetable ferments might not prove beneficial, I tried 

 extract (juice) of fresh pineapple, and of fresh apple. A4 was 

 put into dilute pineapple juice July 27. The reaction was well 

 marked, as shown by decided increase of movement and by three 

 divisions in the ensuing 48 hours. The experiment was repeated 

 the next day with a like result. It was repeated again August 3, 

 but was unsuccessful, the organisms dying two days after treat- 

 ment. The stimulation was temporary in all cases, and it should 

 be noted that the organisms were in a period of increasing vitality 

 when the first pineapple treatment was given (see Diagram I). 



^ The hay infusion was made every day, the same amount of hay and water being 

 taken each time and raised to the boiUng point. This method was never varied 

 during the entire period of the cultures and the salt content of the water, as shown 

 by weekly analyses, did not vary beyond a very slight fraction of one part to one 

 hundred thousand. 



