EFFECT OF TEMPERATURE 



45 



thread to the lever. The tension on the muscle may be varied by altering the 

 weight w. The electrode wires from the secondary coil are connected (1) to 

 the pin fixing the lower end M, and (2) by a very fine light wire, n, passing 

 through the upper end of the muscle. With this apparatus each twitch of 

 the muscle pulls the lever downwards. The magnification should be about 

 threefold or a little higher. The temperature of the muscle can now be 

 altered at will by bringing up a 

 small beaker containing a fluid 

 at the required temperature, so as 

 to immerse the muscle and the 

 vertical limb of the L-piece. The 

 immersion fluid may be normal 

 saline made with tap water instead 

 of distilled water, though it is bet- 

 ter to employ defibrinated ox-blood 

 which has been diluted with four 

 times its balk of normal saline 

 solution, for it is found that the cha- 

 racter of the contraction is very 

 markedly altered if a muscle be 

 soaked in normal saline for any 



Fig. 48. — Apparatus for Varying the 

 Temperatures of a Muscle by Immersion. 



length of time. Having set up the muscle immerse it in fluid at about 0° C. for 

 three or four minutes, and then remove the fluid and record a twitch in the 

 usual way. Without removing the writing point from the surface, again im- 

 merse the muscle, having previously warmed the beaker of fluid by placing 

 it in warm water until its temperature has risen to 5° C. In three minutes 

 remove the beaker and, if necessary, accurately adjust the writing point to 

 the level of the previous abscissa, and then record a second twitch. 



Repeat this for several higher temperatures, when a tracing similar 

 to that of fig. 49 will be obtained. This tracing was given by a 

 hyoglossus, the drum moving at a rapid rate. The various points in 

 the curves should now be examined and the necessary measurements 

 arranged in tabular form, as has been done in the following table for 

 the curves of fig. 49 : — 



In this table all the time measurements are recorded in o/^ths of 

 a second, and for the height of twitch the highest point of the tracing 

 from the abscissa line in millimetres. The amount of contraction is 

 therefore obtained by dividing these last figures by 3, the amount 

 of magnification. As the load was the same in all cases the total 

 work in each case is proportional to the figures of the fifth column. 



