The influence of electrical stimulation on the ACh-like activity of the cat’s superior cervical ganglion and the isolated frog’s heart.

Usually, attempts to demonstrate the physiological function of a substance are made after this substance has been shown to be present in the animal body or tissue. In the case of acetylcholine (ACh), the sequence of events was quite different, for, it will be seen that the physiological role of ACh had been suggested long before its discovery in animal tissue. It is generally believed that two different physiological events occur innerve activity: a) conduction, i.e. propagation of the nerve impulse in the nerve fibers and, b) transmission, a biochemical process that occurs at nerve endings or synapses. The fundamental findings on which these concepts were based can be traced as far back as 1843