I NVESTIGATION of the process of salivary secretion in the human being has been complicated by an apparent large variability in the rate of secretion not only as applied to large numbers of individuals but even for a single individual during a relatively short period of collection under seemingly constant conditions."' 2 Recent workers have attempted to control this variability by collecting for study the so-called "resting saliva," that is, saliva secreted by a fasting subject under standardized conditions of rest.2-5 Collection of saliva under such conditions of reduced external stimulation has succeeded only partially in reducing this variability in the rate of salivary flow.The crucial question, on which the cause and possibility of control of variability in secretion rate would seem to hinge, is whether salivary secretion in the human being occurs spontaneously or only in response to nervous or humoral stimulation. If secretion occurs spontaneously, then measurement of the rate of secretion under conditions of rigid control of external stimulation may give a true rate of flow of resting saliva. Individual variations and variability within a group would then have to be accepted as a real characteristic of the secretion process.However, if secretion does not occur spontaneously, then there is no true resting saliva, and the secretion collected under so-called resting conditions results, nonetheless, from stimulation. Variability in secretion rate would then reflect variations in intensity of stimulation, either internal or external, and would be extremely difficult to control. The basic question of whether salivary secretion in the human being occurs spontaneously or only in response to nervous or humoral stimulation has not up to the present time received a full or satisfactory answer based on experimental data. The early observations of Mitscherlich6 and of Zebrowskij made on isolated human subjects with fistular openings of a parotid duct, indicate that no measurable secretion by the parotid gland occurs in the absence of stimulation. The experiments of Lashley,8 which involved collection of the secretion of the parotid glands from normal subjects by the use of parotid cups, reveal that, under all ordinary conditions of rest while in the