ANIMAL AND VEGETABLE 143 



I do not know what the percentage of alkali in the cell-eon- 

 tents may be. In any case there must be a certain amount 

 of electrolysis due to the body current and irrespective of 

 intra-ceiiular action. In blood plasma sodium is present to 

 the extent of about 0-334, potassium 0-032, and chlorine 

 0-364 per cent. 



As regards rigor, or cessation of protoplasmic move- 

 ment in plants, Sachs gives the following information : 



(1) Temporary cold-rigor occurs in the motile organs 

 of Mimosa pudica, when the temperature remains for some 

 hours below 15 C. The lower the temperature falls below 

 15 C. the more rapidly the rigor sets in. 



(2) Temporary heat-rigor occurs in Mimosa, in moist 

 air at 40 C. within one hour ; in air at 45 C. within thirty 

 minutes ; in air at 49-50 C. within a few minutes. The 

 irritability returns after a few hours in air at a favourable 

 temperature. 



Rigor is also caused by the withdrawal of oxygen ; 

 when brought into the air' the plant again becomes motile. 

 Irritability disappears in hydrogen and nitrogen in carbon 

 dioxide and ammonia, but returns on free exposure to air. 

 Carbonic oxide gas mixed with air to the extent of twenty 

 to twenty-five per cent, destroys the irritability. 



" The vapours of chloroform and ether suspend the 

 irritability of the motile organs (for variations of light 

 also), without destroying the life, if the effect does not 

 continue too long. 



" Temporary rigor due to electric influence was found 

 by Kabsch to occur in the gjjhostemium of Stylidium. A 

 feeble current acted as a stimulus like vibrations ; a 

 stronger one caused a loss of irritability, which returned 

 again, however, after half an hour." 



