“…One of the most sensitive bioassay methods is provided by the exposed and excised heart of the quahog, or clam, Venus mercenaria. 9 This tissue will readily exhibit inhibition by concentration of acetylcholine as low as one part in 10" 10 • By taking advantage of this extremely sensitive method it has been possible to re-examine the question of transmitter in perfusates of dog muscle, and it has been demonstrated that acetylcholine is present in both normal and denervated muscles. 10 This finding, at first glance, appears to throw doubt on the chemical-transmitter theory, a theory that has stood the test of more than 20 years and is now almost universally accepted.…”