Ever since its discovery in 1742 the carotid body has remained an organ of mystery. Originally described as a ganglion, it was subsequently regarded as a gland, chromaffin paraganglion and non-chromaffin paraganglion. In 1928 it was shown to be a chemoreceptor with close associations with the function of baroreception in the adjacent carotid sinus and perhaps within its own substance. These discoveries led physiologists to embark on a series of elegant experimental studies on a number of animal species which have, however, so far failed to identify the transducer for detection of changes in...