The anim als were p h o to g rap h ed ag ain st a sq u ared background, an d p rin ts m ade w ith th e squares enlarged to th e sam e size. E ach anim al w as th e n c u t o u t from th e p rin ts an d all m o u n ted on squ ared p a p e r a n d rep h otographed. R elativ e sizes an d body proportions can be com pared. M ethod of p h o to g rap h y a n d rep ro d u ctio n as in P la te 14. 612.313The secretion of protein m aterial in the parasym pathetic subm axillary saliva This paper deals with a study of the secretion of protein material by the submaxillary gland of the cat in response to electrical stimulation of the chorda tympani nerve. In the attempt to make a more generous use of certain advantages offered by physical methods in research on the digestive glands, the submaxillary gland was chosen for the initial investigation because of the relative ease of physiological experimentation. The study is characterized by (1) the use of quantitative spectroscopic methods of analysis which permit an extension in the range of the investigation over that possible with a purely chemical procedure, and (2) the application of mathematical analysis in the interpretation of the results.

Our experiments have shown that it is possible by the method of degeneration to separate the vasoconstrictor and secretory fibres from the special motor fibres for the submaxillary gland in the cervical sympathetic nerve of the dog. To achieve this it is necessary to perform the experiment a certain number of hours (generally about 90 hours) after aseptic section of the vago‐sympathetic nerve in the neck. The flow of saliva produced by stimulation of the partly degenerated sympathetic nerve after chorda tympani action may be explained by the presence in the nerve of special fibres innervating contractile elements of the submaxillary gland. Degeneration in these fibres is probably a slower process than in the true secretory and vasoconstrictor fibres, and their effect may be observed by isolation under proper conditions. Neither the reflex output of adrenaline nor the general and local vascular changes in the gland can be considered responsible for the outflow of saliva under the influence of the partly degenerated sympathetic nerve. Further, the response of the sympathetic nerve to electrical stimulation cannot be attributed to the effect of the current on the superior cervical sympathetic ganglion, because stimulation of the nerve does not produce either a true secretion or constriction of the blood‐vessels of the gland. The nature of the contractile elements that are activated by the motor sympathetic fibres is unknown. Sinelnikoff (1921) established the fact that the motor function of the partly degenerated sympathetic nerve is not abolished by atropine, and Mackay (1927) demonstrated that histamine acts on these contractile elements. From these conclusions and the results of the experiments reported here, it is clear that the contractile elements remain under the control of the sympathetic nerve. 1. The cervical sympathetic nerve in the dog supplies the submaxillary gland with vasomotor, secretory, and motor fibres. 2. The vasomotor and secretory fibres may be separated from the motor fibres by the method of partial degeneration of the sympathetic nerve. 3. Stimulation of the central end of the vagus, about 90 hours after aseptic section of the vago‐sympathetic nerve in the neck, does not produce vasoconstriction in the submaxillary gland. The secretion also is usually absent or extremely scanty. 4. Stimulation of the partly degenerated sympathetic nerve shortly after chorda tympani stimulation produces a flow of saliva (augmented secretion). 5. Under the conditions of these experiments the augmented sympathetic secretion is a purely mechanical phenomenon, fluid that has been blown back into the gland being pressed out again as a result of stimulation of the partly degenerated sympathetic nerve. 6. In most of the experiments stimulation of the partly degenerated sympathetic nerve increased the blood‐flow through the gland. This effect was not due to changes in the systemic blood‐pressure, which varied in different experiments. No analysis of this phenomenon was attempted. The writer wishes to express his in...