THE NERVELESS MUSCLE 33 



mine at what distance of the secondary coil from the primary a 

 response is obtained in each case. 



The conclusion is that neither the nerve fibres, sensory and motor, 

 nor the nerve centres, nor the muscular fibres are affected, 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 contract 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 just above 

 the level of the fluid. This 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 gastro- 

 cnemius. 



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

 in continuity with the main trunk see p. 41. 



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 

 intramuscular 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 separation 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. 35). When the muscle 

 contracts, its swelling raises first the lever nearer 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-Eeymond key 



3 



