mucus which it secretes? If it makes its secernable products, what materials does it abstract from the blood for the purpose of their manufacture? Does it use the whole of these materials, whatever they may be, or does it use part only and return the residue to the lymph? Does it make its products only when it is actively secreting, or is it always making them, and storing them in its cells in order that it may have a supply to discharge when called upon by the stimulation which results from the presence of food in the mouth? Is their discharge merely a washing out due to the rush of fluid which occurs when the bloodvessels are dilated, or can the gland-cells expel their products in response to nervous action? In what way do the nerves of the gland influence secretion? Do they call for increased production, or increased output, or both? These are some of the problems which the exposed situation of the submaxillary gland allows physiologists to tackle. By means of a very simple operation, the ducts of one or both parotid or submaxillary glands can be brought to the skin, and made to pour their secretions on to the surface instead of into the mouth. The flow under various circumstances can be watched. The saliva can be collected and measured. The nerves of the submaxillary gland are easily isolated. A nerve leaves the seventh (or facial), crosses the drum of the ear, comes out through a minute crevice in the skull, and runs for some little distance as a separate nerve before it applies itself to the lingual branch of the fifth, which runs along the side of the tongue. Owing to its passage across the tympanic cavity (drum of the ear), it is termed “chorda tympani.” As its fibres are very small, they can be recognized wherever they form a part of the lingual nerve. They leave the lingual to go to a ganglion, the submaxillary ganglion, from which the gland is supplied. The gland also receives branches from the sympathetic nerve which ascends the neck. The last-named branches accompany the facial artery. Stimulation of either of these nerves causes the gland to secrete. The flow of saliva which follows stimulation of the chorda tympani is much more copious than that which follows stimulation of the sympathetic, and as a rule it contains far less organic matter, although about the same amount of mineral salts. Under normal conditions the activity of the chorda tympani is brought into play in a reflex manner by impulses which travel up the nerves of taste (the lingual and glosso-pharyngeal) to the cerebro-spinal axis; but almost any other nerve will serve as an afferent path. The gland may also, as we shall presently explain, be called into activity by the cortex of the brain.