AUXETICS 37 



Adds. The free forms are very readily affected 

 by citric acid, 0*05 per cent, being sufficient to kill 

 and disorganise them. Amosbse will, however, 

 excyst on jellies containing as much as 0'2 per 

 cent. HC1. The cysts will tolerate 2-per-cent. 

 HC1 (31'8-per-cent. HC1) and 3-per-cent. lactic 

 acid for at least a week. Acids delay the diffusion 

 of stain into the living cell. 



EXPERIMENTS WITH AUXETICS AND KINETICS 



Asparagin (auxetic}. This was the first auxetic 

 selected, because its ready solubility in water 

 permits of a larger range of concentration being 

 examined than most of the other known auxetics. 

 The moist-chamber method (Method B) was used. 

 On a 1-per-cent. asparagin l jelly excystation took 

 place after twenty-four hours, bacteria, yeasts, and 

 moulds growing profusely, particularly the last two. 

 On a 3-per-cent. jelly (boiled for five minutes, 

 slightly acid) excystation took place on the second 

 day, with a slow development of moulds, bacterial 

 growth being almost arrested. On the third day 

 the whole medium was swarming with minute, 

 very active, free forms of the amoeba (fig. 13). 

 They were very difficult to distinguish, and it 

 was only their movement which attracted attention 

 to them. It was impossible to follow their changes 

 in shape owing to their extreme motility. A few 

 very small cysts were also present. This culture was 

 closely watched, the growth of moulds continuing 



1 Added to the jelly when cool ; unboiled solutions of asparagin are 

 faintly acid to litmus, while boiled solutions are distinctly acid owing 

 to hydrolysis and formation of aspartic acid. 

 IV 3* 



