356 THE OUTGO OF ENERGY 



2. Place the adjustable rod in the hole nearest 

 the iron support (isometric arrangement). Stimu- 

 late the muscle (1) with the tetanizing current 

 of the inductorium ; (2) by voluntary impulse. 



It will be seen that the energy set free by the 

 natural stimulus is much greater than when the 

 muscle is stimulated artificially. 



SMOOTH MUSCLE 



Spontaneous Contractions. Make two cuts, 

 5 mm. apart, through the frog's stomach at 

 right angles to the long axis. Pass a bent hook 

 through the ring (i. e. through the cavity of the 

 stomach), and fasten the hook in the muscle 

 clamp. Pass a second hook around the lower 

 margin of the ring and attach it by means of a 

 fine copper wire to the straw of the heart lever 

 (Fig. 53). Contraction of the circular fibres can 

 thus be made visible. Bring the writing point 

 against a drum revolving about once an hour. 

 Wrap filter paper saturated with normal saline 

 solution about the muscle ring. Keep this 

 thoroughly moist. Proceed to the remaining ex- 

 periments, observing the stomach preparation 

 from time to time. 



Spontaneous rhythmic contractions will appear. 

 Note the changes in tonus. 



