80 CONSCIOUS NERVOUS OPERATIONS 



and the insertion can be made out. The respective share wnich each 

 muscle takes in the movements of the limb can be shown by touch- 

 ing the individual muscles with the electrodes of a weak galvanic 

 battery. The change in shape of the muscle during contraction will 

 also be very well shown. 



18. Relaxation and Contraction of Muscles. Extend one arm nearly 

 straight from the shoulder. Then bend the arm at the elbow, draw- 

 ing the hand up to the shoulder. With the other hand can be felt 

 the changes in the form of the biceps muscle, as it relaxes and con- 

 tracts. If the arm be bared the changes in form of the muscle can 

 be seen. The tendon of the biceps at the elbow can also be seen. 



19. Gross Structure of Muscle. Obtain a piece of boiled corned 

 beef, and dissect it with needles. The larger and smaller bundles of 

 muscle fibers can be easily differentiated. By aid of a lens even the 

 separate fibers can be isolated. Observe between the bundles and 

 fibers the whitish connective tissue, in life tough and fastening the 

 bundles and fibers together, but now softened in boiling. 



20. Functional Difference between Voluntary and Involuntary Muscle. 

 If the abdominal cavity of the frog experimented upon in a preced- 

 ing section be opened and the electrodes applied to the stomach and 

 intestines, the difference between the movements of voluntary and 

 involuntary muscle will be clearly demonstrated. 



21. Fatigue of Muscle. On applying repeated electric shocks 

 directly to a frog's muscle, or indirectly through its nerve, the re- 

 sponses are seen to become more and more feeble. But after a period 

 of rest, the muscle responds as vigorously as ever. 



22. Nerve Endings in Muscle. While the tracing out of the final 

 nerve ends in muscle must be left to the histological expert, yet 

 the general relations of motor nerves to muscles can be very easily 

 shown in the frog. Branches of the sciatic nerve can be traced out 

 to the muscles of the leg (Fig. 8, p. 18), and by electrical stimulation 

 the functional relation between nerve and muscle can be shown. 



23. Rigor Mortis. Observe in a frog, just after decapitation, that 

 the muscles are soft and relaxed. Shortly after the tissues have com- 

 pletely lost their vitality, the muscles will be found to be hard and 

 contracted. The limbs which may have been bent at the joints and 

 limp, are now straight and rigid. Death rigor or rigor mortis has set 

 in. After some time, the muscles again become flaccid and putrefac- 

 tion soon begins. Place fresh muscle in hot water, and observe that 



