982 7. MERCURIALS 



was not the criterion, but cessation of movement, since no attempt to reac- 

 tivate was made. When the log of survival time was plotted against log 

 (Hg++), two linear segments were obtained, which led Gause to conclude 

 that two different processes are responsible for the paralysis. The treat- 

 ment is based on an equation of the type 1-12-89 and plotting as in Fig. I- 

 12-38. A break in the curve would suggest a change of the exponent n and, 

 since it is possible for one process or response to exhibit different values of 

 n, it is not necessary to conclude that Hg++ kills by two processes. High 

 sensitivity of paramecia to Hg++ was also noted by Calcutt (1950), who 

 found 0.001 raM to paralyze within 6-14 min depending on illumination. 

 Paralysis of Colpidium colpoda occurs in 3 min after exposure to 0.00087 

 mM PM (Walker, 1928). Some of the variations in sensitivity are due to 

 the strains used, and probably some to the media in which the ciliates were 

 suspended. It is probably safe to say that ciliary movement is very sensitive 

 to mercurials and is stopped within a few minutes by concentrations in the 

 range 0.001-0.01 mM. Reversal of ciliary beat by Hg++ is not observed 

 (Oliphant, 1942). The classic death rate curves for Colpidium exposed to 

 0.2 mM Hg++ and their relation to population variation were discussed 

 previously (page 1-593 and Fig. 1-12-36). 



The effects of the mercurials on ameboid movement are interesting be- 

 cause of the possible bearing on muscle contractility. Reznikoff (1926) used 

 rather high concentrations of Hg++ and consequently found only a pinch- 

 ing off of the region into which the Hg++ was injected (0.62 mM), or a 

 break in the membrane (up to 10 mM), or an immediate gelation or coagu- 

 lation of the protoplasm (up to 200 mM). Kappner (1961) used mersalyl 

 since this mercurial has been a favorite with myologists, and the changes 

 he observed in amebas with increasing concentration are worth describing 

 briefly. With 0.001 mM mersalyl there are no immediate changes but after 

 several days some damage is evident. At 0.01 mM there is restriction of 

 normal pseudopodial response and fewer pseudopods are formed, while 

 clumping of the cytoplasmic crystals occurs. At 0.1 mM the pseudopods 

 withdraw, the ceUs soon form numerous small pseudopods at the end of 

 which appear tiny spheres, the cortex appears to be thicker, and eventually 

 the cells round up. At 1 mM the response is not so specific, the surface 

 bubbles, the cells round up, and soon the membrane dissolves. Higher con- 

 centrations produce vacuolization and cytolysis. Abe (1963) reported a sim- 

 ilar study but with p-MB to which amebas seem to be more sensitive than 

 to mersalyl, since 0.1 mM causes cytolysis within 8 min. Further investiga- 

 tion of this interesting problem is warranted and a closer analysis of the 

 effects of low concentrations on the sol-gel transformation might provide 

 useful information on the role of SH groups in protoplasmic movement. 



