ACCOMPLISHMENT OF LABOUR. 37 



A slight pressure on the handle of the lever d is, there- 

 *fore, sufficient to produce or to put an end to the te- 

 tanic condition at the will of the operator, thus allowing 

 more accurate study of the muscle processes. 



We have now noticed muscle in two conditions : in 

 the ordinary condition in which it usually occurs either 

 within the body or when taken from the body, and in 

 the contracted condition which results from the appli- 

 cation of certain irritants. The former condition may 

 be spoken of as the rest of the muscle, the latter as the 

 action of the muscle. Muscular action occurs in two 

 forms, one of which is a sudden temporary shortening 

 or pulsation, while the other is an enduring contraction 

 or tetanus. The latter, on account of its longer dura- 

 tion, is more easily studied. In many cases it is a 

 matter of indifference whether pulsating or tetanised 

 muscle is examined. In the following investigations 

 we shall therefore employ sometimes one, sometimes 

 the other, method of irritation. 



3. On attaching weights to a muscle, the latter is 

 capable of raising these weights so soon as it is set in 

 motion. It raises the weight to a certain height, and 

 thus accomplishes labour which, in accordance with 

 mechanical principles, can be expressed in figures by 

 multiplying together the weight raised and the height 

 to which it is raised. This height to which the weight 

 can be raised, which may be called the height of ele- 

 vation of the muscle, can be measured by means of the 

 myograph already described. On attaching a weight 

 to the lever of the myograph, the muscle is imme- 

 diately extended. The pencil must now be brought in 

 contact with the glass plate of the myograph, and 

 the muscle must be made to contract by opening the 



