CHAPTER VI 



THE NERVELESS MUSCLE 



Action of curari. The brain of a frog is destroyed by passing a 

 sharp splinter of wood through the occipital foramen after cutting 

 through the skin and occipito-atlantoid ligament. The blood-vessels 

 of one leg are ligatured, care being taken to avoid injuring the accom- 

 panying sciatic nerve. Or the leg can be tightly tied round with a 

 tape so as to stop the circulation within it. A drop or two of one per 

 cent, solution of curari is now injected under the skin of the back. 

 After a short time the drug will have penetrated to all parts of the 

 body except the ligatured leg. 1 The following observations and 

 experiments may then be made : 



1. Notice that all the muscles are paralysed except those of the 

 ligatured limb. 



2. On tapping any of the paralysed parts the foot on the ligatured 

 side is moved i.e., the conducting power of the nerves both sensory 

 and motor, and the reflex functions of the spinal cord are not 

 abolished. 



3. Strip the skin off both legs and isolate both sets of sciatic 

 nerves at the back of the abdomen. Tie their upper ends and cut 

 them away from the vertebral column. Excite both sets of nerves 

 high up, placing them upon the same electrodes and observe the differ- 

 ence of effect. Excitation of the nerve of the limb which has been 

 exposed to the poison produces no contraction of its muscles ; ex- 

 citation of the nerve of the ligatiired limb produces the usual effect. 

 Now stimulate the muscles of the two limbs, applying the electrodes 

 directly to them. The muscles of the poisoned lirnb react like those 

 of the normal limb, but the liminal stimulation 2 is greater. Deter- 



1 This method is applicable to the study of the action of drugs in general 

 on nerves and muscles. 



2 The stimulation which is only just effective, i.e. the least stimulation 

 which is responded to. 



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