STIMULI AND THEIR ACTIONS 



395 



from which warming cannot restore life. This minimum of 

 temperature lies of course with different organisms at very different 

 heights. Thus, as has been seen, Klihne showed that Ammha dies 

 upon freezing, that is, upon being cooled to a little below 0° C. ; 

 while Pictet found for Bacteria that they could endure cooling to 

 more than — 200° C. without losing their vital capacity.^ The 

 question whether in any living substance a point is ever reached by 

 cooling where the vital processes are at a complete standstill without 



Fig. 183. — Forms of the body of JrrKeba Umax at different temperatures. A, At 25° C. ; the 

 amcebse have an extended wedge-shape, and show active protoplasmic streaming. B, At 

 40° C. ; the amcebse have assumed a spherical form, and are in heat-rigour. C, At 2° C. ; the 

 amoebae show a lumpy cell-body, from which numerous small pseudopodia project ; move- 

 ment is noticeable only after very long-continued observation. 



the vital caiiacity being extinguished, is at present no more 

 decided than the same question regarding narcosis. Cold-rigour 

 and narcosis are wholly analogous states : in both, vital processes 

 are not perceptible, from both by restoring the normal conditions 

 the living substance is restored to life, and from both by inten- 

 sifying the unusual condition, i.e., by deeper narcosis and further 

 cooling, it passes over into irreparable death. This latter fact, that 

 increased narcosis and cooling abolish the vital capacity of 

 paralysed organisms, ought rather to speak in favour of the view 



1 Cf. p. 290. 



