496 



APPENDIX 



a medium speed and keep this speed throughout the experiment. Make 

 two or three of these curves. Now light the gas-burner (having its 

 smokeless flame not over 3 cm. high) and place it under the outer end of 

 side-tube. When the temperature has risen 5 cause another maximal 

 break shock and record as before. Repeat this for every 5 rise of 

 temperature, having the series of eight or nine curves all on one drum. 

 As the temperature reaches 45 the muscle begins to go into heat-rigor, 

 as is shown by its slight irregular contractions. Now have the drum 

 revolve at a slow speed so as to obtain a graphic record of this, the final 

 dying contraction of the muscle, above the abscissa line. 



FIG. 277 



Apparatus as set up by students to study the work done by a frog's cross-striated muscle. 



Compare the shape of the various curves as regards (a) the decreasing 

 lengths of the latent periods ; (b) the increasing quickness of contraction; 

 (c) the increasing quickness or relaxation ; and (d) the increasing heights 

 of the lever's rise, save at first, until near the end when the extent of the 

 contraction somewhat decreases (as also the relaxation) as the muscle 

 begins to stiffen with the heat. 



The degree of heat of a muscle has much to do with the various 

 analyzed parts of the contraction-movements. (1) The latent-period 

 is shortened by increasing the temperature up to about 35, it being per- 

 haps half as long as at 5. (2) In general terms, the amount of shorten- 

 ing of the muscle is increased by the upper limit of heat (as shown by 

 height of the myogram), this increase being 40 per cent, or so over that 

 of the muscle at 5. (3) Generally speaking, the contraction time is 



