1901.] on the Response of Inorganic Matter to Stimulus* 



617 



lever arrangement, by which the contracting muscle writes down the 



history of its change, and recovery from that change. The record 



may be made on a travelling band of paper, which is moving at a 



uniform rate (Fig. 1). This autographic record gives us the most 



accurate information as to the characteristic properties and condition 



of the muscle. It gives us, too, its history and all its peculiarities. 



Just as one wave of sound is distinguished from 



Characteristics another by its amplitude, period, and form, so are 



of the Response the curves of different muscles distinguished. For 



Curve : example, the period of tortoise muscle may be as 



(1) Amplitude, large as several seconds, whereas the period for 



(2) Period, the wing of an insect is as small as ^^th of a 



(3) Form. second. In the same muscle, again, the form of 



the curve may undergo changes from fatigue, or 



from the effects of various kinds and quantities of drugs. In the 



autographic record of the progressive death of a muscle, the writing 



is bold and vigorous at first, 



but grows lethargic on the 



approach of death. In some 



strange way the molecules lose 



their mobility, rigidity super- 

 venes, and the record of the 



dying muscle comes to an end. 



We may thus find out the 



effects of various external influ- 

 ences by studying the changes 



of form of the muscle curve. 

 We may stimulate 



Different the living sub- 



Forms of stance in various 



Stimuli : ways — by light, 



Electrical, or by thermal, 



Mechanical, chemical, electri- 

 cal, or mechanical 



stimuli. Of these, the electric 



means of stimulation is the 



most convenient, whereas the 



mechanical gives rise to the 



fewest complications. With 



regard to this response of 



living substances, the most im- 

 portant matters of study are 



the responses to single stimu- 

 lus and to rapidly-succeeding 



stimuli, and the modification of 



response by fatigue and drugs. 



A single shock causes a twitch, but the muscle soon recovers its 



original shape. The rising portion of the curve is due to contrac- 



Fig. 1. — Mechanical Lever Eecorder. 

 The muscle M with the attached bone is 

 securely held at one end, the other end 

 being connected with the writing lever. 

 Under the action of stimulus the contract- 

 ing muscle pulls the lever and moves the 

 tracing point to the right over the travel- 

 ling recording surface P. When the muscle 

 recovers from contraction, the tracing point 

 returns to its original position. See on P 

 the record of muscle curve. 



