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 accompanying 

 sciatic nerve. Or the leg, with exclusion of the nerve, can be tightly 

 tied with a tape to stop the circulation. A drop of 1 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 

 (i.e., non-paralysed) side is moved therefore 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 ligatured limb produces the usual effect. 

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

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

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

 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, 



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

 the nervous and muscular systems. 



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

 is responded to. 



34 



