Diagram of the path of the inborn unconditioned reflexes from the mouth cavity to the salivary gland in a dog. The figure shows that the result of excitation of the wet tongue is transmitted along the centripetal nerve to a centre in the medulla oblongata, whence impulses are directed to the salivary gland.
A dog prepared for experiment with a fistula of the duct of the parotid salivary gland, and a funnel for conducting the falling drops.
From the scientific film The Nervous System as reproduced in Frolov, Y. P. (1937) Pavlov and his School; The Theory of Conditioned Reflexes. Kegan Paul, Trench, Trubner & Co. Ltd. Carter Lane E.C.