AMOEBINA 451 



all dead on the 13th day (Kuenen and Swellengrebel ; a). Viable for 

 25 days (Thomson and Thomson; a). Cysts in running water for 15 

 days, excysted in pancreatic juice (Penfold, Woodcock and Drew). 

 Viable for 30 days (Wenyon and O'Connor; a) ; for 5 weeks (Dobell) ; 

 for 153 days (Boeck; a). Alive for 10 and 17 days at 16-20° and 0°C. 

 respectively (Yorke and Adams; 6); for 3, 10, 30, and 90 days at 

 30°, 20°, 10° and 0°C. respectively (Chang and Fair; b). 



3. Cysts in relation to high temperatures. Cysts are killed at 

 68°C. in 5 minutes (Boeck; a); at 50°C. in 5 minutes (Yorke and 

 Adams; 6). Dipping in boiling water for 5-10 seconds kills the cysts 

 (Kessel; a). 



4. Cysts in relation to desiccation. Desiccation kills cysts instantly 

 (Kuenen and Swellengrebel; Wenyon and O'Connor, Dobell, etc.). 

 Therefore, the cysts carried in dust are most probably not viable 

 under ordinary circumstances. 



5. Cysts in relation to chemicals. 



HgCl 2 . 0.1% solution kills cysts in 4 hours (Kuenen and 

 Swellengrebel; a) ; kills readily (Lin; 6). 1 : 2500 solution kills 

 cysts in 30 minutes at 20-25°C. (Yorke and Adams; 6). 



Creolin. 1 :250 solution kills cysts in 5-10 minutes (Kuenen and 

 Swellengrebel; a). 



Alcohol. 50% alcohol kills cysts immediately (Kuenen and 

 Swellengrebel; a); in one hour (Kessel; a). 



Formaldehyde. Cysts treated in 1% solution for 4 hours were 

 apparently dead, though not stained with eosin (Wenyon 

 and O'Connor). 0.5% solution kills cysts in 30 minutes at 

 20-25° or 37°C. (Yorke and Adams; b). 



Cresol. 1:20, 1:30, and 1:100, killed the cysts immediately, 

 in one minute and in 30 minutes respectively (Wenyon and 

 O'Connor; a). 



Phenol. 1:40 and 1:100 killed cysts in 15 minutes and 7 hours 

 respectively (Wenyon and O'Connor; a). 1% solution of 

 phenol or lysol kills cysts in 30 minutes at 20-25° or 37°C. 

 (Yorke and Adams; b). 



HC1. 7.5% solution at 20-25°C. and 5% at 37°C. kill the 

 cysts in 30 minutes (Yorke and Adams; 6). 



NaOH. 2.5% solution kills cysts in 30 minutes at 20-25° or 

 37°C. (Yorke and Adams; 6). 



Chlorine. 1:10,000 solution did not have any effect on cysts 

 after several hours (Wenyon and O'Connor; a). 0.2% and 

 0.5% solutions kill the cysts in 7 days and 72 hours respec- 

 tively (Kessel; a). 0.5% and 1% solutions kill the cysts in 



