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not during contraction, and hence the probability is that electricity 

 has been discharged when a muscle contracts on being touched by a 

 needle, a probability which is supported by the analogy which exists 

 between the structure of muscle and the structure of the electrical 

 organ of the Torpedo, and between the circumstances producing 

 contraction on the one hand and discharge on the other (Owen, 

 Faraday, and others); and (2) because the movements of the sto- 

 mach, or uterus, or any other viscus are not to be accounted for on 

 the supposition that the contractions are stimulated by the contents 

 of the viscus ; thus the food accumulates and the stomach expands 

 until the appetite is satisfied, and contraction does not happen until 

 the preliminary processes of digestion are at an end, and thus also the 

 child grows and the uterus expands, and labour pains do not begin 

 until the growth of the child is completed, and the stimulus of that 

 growth suspended. 



(e.) That heat and cold do not stimulate contraction, because con- 

 traction does not happen until the natural polar action of the muscle is 

 suspended, an event which happens equally under either extreme of 

 temperature, and thus the muscle would seem to contract because 

 the heat or cold extinguishes that polar action of the muscle which 

 antagonizes contraction. 



(/.) That light cannot cause contraction, (1) because it exercises 

 a directly opposite influence upon the irritable cushions of the sensi- 

 tive plant ; and (2) because it is as easy to agree with Bichat, and 

 suppose that light expands the curtain of the iris, as that it causes 

 contraction in sphincter-fibres surrounding the pupil, which fibres 

 have no existence. 



(g.) That chemical and mechanical agencies do not stimulate con- 

 traction, because contraction does not happen until the agent has de- 

 stroyed that polar action of the muscle which antagonizes contrac- 

 tion (Eckardt). 



It is argued, also, that the action of the will upon muscle is not 

 necessarily that of a stimulus, for the will may act by withdrawing 

 something from the muscle as well as by communicating something 

 to the muscle, and, if so, then the previous considerations enhance 

 the probability that it acts by withdrawing something. 



In the course of the argument it is further shown that this con- 



