## Core Concept
The discovery of chemicals being released by nerve terminals is a fundamental concept in neuroscience, specifically in the field of neuropharmacology and neurotransmission. This concept revolves around the understanding that neurons communicate with each other through chemical signals, known as neurotransmitters.

## Why the Correct Answer is Right
The correct answer, **C. Otto Loewi**, is attributed to the discovery of chemical neurotransmission. In 1921, Otto Loewi conducted a series of experiments on the vagus nerve of frogs, demonstrating that stimulation of the vagus nerve caused the release of a chemical substance (later identified as acetylcholine) that could affect the heart rate of the frog. This groundbreaking experiment provided direct evidence for chemical neurotransmission and earned Loewi the Nobel Prize in Physiology or Medicine in 1936.

## Why Each Wrong Option is Incorrect
- **Option A:** Although **A. Henry Dale** also made significant contributions to the field of neurotransmission, his work built upon Loewi's discovery. Dale identified acetylcholine as a neurotransmitter and characterized its role in the nervous system, but he did not make the initial discovery of chemical release by nerve terminals.
- **Option B:** **B. Harvey Cushing** was a renowned neurosurgeon and physiologist, but his work primarily focused on the field of neurosurgery and the study of intracranial pressure. He did not contribute to the discovery of chemical neurotransmission.
- **Option D:** **D. Walter Cannon** made significant contributions to the understanding of the sympathetic nervous system and the role of adrenaline (epinephrine) in the "fight or flight" response. However, his work did not involve the discovery of chemical neurotransmission.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **Otto Loewi's experiment** demonstrating chemical neurotransmission involved stimulating the vagus nerve and observing the effect on heart rate, which led to the identification of acetylcholine as a neurotransmitter. This concept is crucial for understanding how neurons communicate and is a foundational element in neuropharmacology.

## Correct Answer: C. Otto Loewi