Impulse frequency in secretory nerves of salivary glands.

1. In dogs under pentothal anaesthesia the submaxillary duct was exposed in the neck and a polythene tube tied into it. During the following days the dogs were examined repeatedly, standing in a frame. The highest rates of submaxillary secretion evoked by introducing various foodstuffs or rejectable substances into the mouth were estimated. Finally, the dogs were anaesthetized and the rates of salivary flow recorded during electrical stimulation of the chordalingual nerve at different frequencies.2. The frequency-response curve for electrical stimulation has a steep slope up to a frequency of 10/sec, where a salivary flow at a rate of about 90% of the maximal is evoked.3. The fastest secretion that is obtained reflexly on feeding corresponds to a flow which in different experiments varies between 4 and 8 shocks/sec. The very rapid secretion caused by rejectable substances can be reproduced by stimulating at 10-30/sec.4. In similar experiments on the parotid gland foodstuffs were often, and rejectable substances always found to cause a salivary flow at a rate which exceeded that obtained on maximal stimulation of the auriculotemporal nerve. This supports the view expressed by previous investigators that additional secretory fibres reach the parotid gland of the dog by anatomically unknown routes.