32 THE PHYSIOLOGY OF MUSCLE AND NERVE. 



therefore, that two different contraction processes are initiated by 

 the stimulus, one much more rapid than the other. Many other 

 facts in physiology speak for this general view that a muscle may, 

 according to conditions, give either a quick contraction (twitch) 

 or a more slowly developing contraction, with a prolonged phase of 

 relaxation (tone contraction). This latter feature constitutes the 

 characteristic peculiarity of the curve of a veratrin contraction. 

 A somewhat similar effect is produced by the action of glycerin, 

 nicotine, etc. We have in such substances reagents that affect 

 one phase of the contraction process without materially influenc- 

 ing the other. As regards the veratrin effect, it becomes less and 

 less marked if the muscle is made to give repeated contractions, 

 but reappears after a suitable period of rest. The peculiar action 

 of the veratrin is, therefore, antagonized seemingly by the chemical 

 products formed during contraction. 



Contracture. The prolonged relaxation that is so character- 

 istic of the veratrinized muscles may be observed in frog's muscle 

 under other circumstances, and is described usually as a con- 

 dition of contracture. By contracture we mean a state of main- 

 tained contraction or, looking at it from the other point of view, 

 a state of retarded relaxation. 



This condition is often exhibited in a most interesting way when a muscle 

 is repeatedly stimulated. In some cases it develops at the beginning of a 

 series of contractions, as is represented in Fig. 14, which pictures the phenome- 

 non as it was first described.* In other cases it appears later on in the curve, 

 preceding or following the development of the state of fatigue. Whenever 

 it occurs the effect is to hold the muscle in a state of maintained contraction or 

 tone, on which is superposed the series of quick contractions and relaxations 

 due to the separate stimuli. When the condition develops early in the func- 

 tional activity of the muscle (Fig. 14) further activity usually causes it to dis- 

 appear, and the condition of the muscle as a mechanism for prompt shortening 

 and relaxation is improved. We have in this fact apparently an indication 

 of one way in which the " warming up" exercise before athletic contests may be 

 of value. When the contraction appears late in the series of contractions 

 it is usually permanent, that is to say, it wears off only as the muscle relaxes 

 slowly from fatigue. Toward the end of such a series the muscle is often 

 practically in a state of continuous contraction, a condition which would 

 nullify its ordinary use in locomotion. It seems possible that certain con- 

 ditions of tonic spasm or cramps which occur during life may involve this 

 process, for example, the temporary cramp that sometimes attacks a player 

 in athletic games, or the curious spasmodic condition known as intermittent 

 claudication, in which the muscles on exercise are thrown into a state of 

 tonic contraction. From the physiological standpoint the phenomenon of 

 contracture when compared with that of the simple contraction indicates the 

 possibility that two different contraction processes may take place in muscle, 

 one involving the state of tone and, therefore, the length and hardness of 

 the muscle, the other controlling the movements proper. This suggestion 

 has been made by a number of authorsf on various grounds. It has been sug- 



* Tiegel, "Pfliiger's Archiv fur die gesammte Physiologic," etc., 13, 71, 

 1876. 



fSee especially Uexkull, "Zentralblatt f. Physiologic/' 1908, 22, 33; also 

 Guenther, "American Journal of Physiology," 1905, 14, 73. 



