In 110 subjects with traumatic severance of secretory nerves, salivation was studied to determine the effect of denervation on gland function. A sequence of responses was found in which an initial hyperpositive response to cholinergic agents was blocked by atropine (stage I); this effect was reversed and increased salivation occurred in both latent (stage II) and overt (stage III) forms of the atropine paradox. The hypothesis suggested is that chemoreceptive cells of parotid membranes include a minimum of five populations of cholinergic receptors which respond differentially to parasympathetic agonists and antagonists.