HEAT DUE TO IONTSATION 27 



of water, and 212,000 calories or units of heat ; in 

 other words, the energy of 16 grammes of methane 

 and 64 grammes of oxygen together is more than 

 that possessed by 44 grammes of carbon dioxide 

 and 36 grammes of water by an amount which would 

 produce 212,000 calories. During muscular action 

 a similar amount of force over and above that 

 which is necessary to produce sarcolactic acid and 

 carbon dioxide produces the contraction and is 

 transformed into heat. 



The effects of ions on contractile tissues have been 

 observed, and Loeb asserts that sodium chloride is 

 a poison to them all. The well-known effects of 

 ions on muscular tissue are masked by the presence 

 therein of organic substances having large molecules, 

 which is regarded as an indication of their com- 

 bination.* Although the ions of sodium and 

 lithium are very similar physically, their physio- 

 logical effects are not equivalent. There is no 

 foreign element so slow to make a noteworthy 

 change in skeletal muscle as lithium ; but when 

 most of the normal sodium in it has been replaced 

 by lithium, it is followed by a characteristic fall in 

 the muscular irritability, f A controversy has 

 existed for some time as to whether the action of 

 contractile tissue is of muscular or nervous origin. 

 The constitution of the environment, as well as that 

 of the tissues, enters into the question ; and many of 

 the arguments about it have been based upon the 

 ionic theory. Loeb J experimented with the medusa ; 



* Stiles and Beer: Amer. Jour. Physiol, 1905, xiv., 133. 

 t Millikin and Stiles : Ibid., p. 359. 

 J Ibid., 1900, iii., 383-393. 



