THE NERVELESS MUSCLE 35 



nor the nerve centres, nor the muscle fibres are paralysed, but that the 

 poison has produced paralysis by severing the connexion between 

 motor nerve fibres and muscle fibres, probably at the end-plates. 



The paralysing action of curari can also be shown by keeping 

 a muscle-nerve preparation in Ringer's solution to which a little curari 

 solution has been added. It will be found that after a time the muscle 

 will cease to respond to stimulation of its nerve, although it will con- 

 tract readily if the muscle itself is stimulated. As a control, another 

 preparation may be taken, and its nerve alone placed in the same 

 solution during the same period, the muscle being supported above the 

 level of the fluid. The preparation will respond to every stimulation 

 of its nerve. 



It is best to use a sartorius muscle-nerve preparation for this 

 experiment on account of the length of time necessary for the curari 

 to penetrate the gastrocnemius. 



For the mode of preparing the sartorius the nerve of which must 

 be kept in continuity with the main trunk see p. 22. 



Muscle- wave. Separate from the remaining thigh muscles the 

 adductor muscles (gracilis and semimembranosus ; see Figs. 28, 29) 

 of a frog which has been poisoned with curari to eliminate the intra- 

 muscular nerves. Leave the attachments to the tibia. Cut this bone 

 through just below these attachments, and also sever the tibia from 

 the femur at the knee joint. It is then easy to complete the separ- 

 ation of the muscles up to their iliac attachments ; a small fragment 

 of the ilium may be cut away and removed along with them. Tie 

 a thread to the tibial and another to the iliac attachment, stretch 

 the muscular mass lightly between these threads, and fasten to the 

 cork by a couple of pins at one end and a pair of pin-electrodes at 

 the other end of the muscle. Allow two long light levers (which can 

 be made of straws, working in simple brass holders capable of being 

 pinned to the cork) to rest upon the muscle near each end close 

 to their fulcra, and let the points of the levers write lightly on 

 the drum, one exactly above the other (Fig. 36). When the muscle 

 contracts, its swelling raises first the lever near to the electrodes, 

 and later the one at the further end. The movements of the levers 

 are recorded upon the drum, and curves are obtained of the swelling 

 of the muscle during its contraction in the same manner as the 

 curves of shortening of the gastrocnemius were obtained in previous 

 experiments. The drum must move at a fast rate, and the levers 

 should be directed obliquely downwards : much more so than in the 

 ordinary method. 



Connect the pair of pin-electrodes with a du Bois-Reymond key 

 (&') in the secondary circuit. Describe an abscissa, and mark the 



