How did Claude Bernard use curare to distinguish nerve-related problems from muscle-related problems?

The 19th-century French physiologist Claude Bernard utilized curare as a precise experimental tool to differentiate between nerve-related and muscle-related physiological mechanisms.12

By observing the effects of the poison, Bernard demonstrated that curare induces paralysis by specifically blocking transmission at the neuromuscular junction—the site where motor nerves communicate with muscle fibers. His experiments revealed that while curare effectively halts this communication, it does not directly impair the conduction of impulses along the nerves themselves, nor does it directly affect the ability of the muscle to contract when stimulated by other means.12

Because of this selectivity, Bernard was able to isolate and identify the neuromuscular junction as the specific site of action, allowing researchers to distinguish between primary muscular disorders and those originating in the nervous system. This work was a significant contribution to the development of experimental medicine, as it moved physiology away from vague concepts like vitalism toward a mechanistic understanding of biological processes.234