LECTURE IV. 



GENERAL SCHEME OF AN INNERVATION MECHANISM 



THE WORK OF THE NERVOUS APPARATUS OF 



THE SALIVARY GLANDS APPETITE, THE FIRST 



AND MOST POTENT EXCITER OF THE GASTRIC 



SECRETION. 



Constituent parts of a complete innervation mechanism The special 

 duty of the peripheral terminations of afferent nerves The specific 

 qualities of nerve cells Analogy between the innervation mechanism 

 of the salivary glands and that of the deeper-lying glands of digestion 

 The exciting agencies of the nervous mechanism of the salivary 

 glands ; their particular properties Differences between the exciting 

 agencies of the different salivary glands Discussion of the sham feeding 

 experiment Mechanical and chemical stimulation of the cavity of the 

 mouth has no effect on the gastric glands The experiment of Bidder and 

 Schmidt relative to psychic excitation of the gastric secretion Conditions 

 for success in this experiment The passionate longing for food the 

 appetite alone brings on the secretory effect in the sham feeding experi- 

 ment. 



GENTLEMEN, As you have learned in the last lecture, and also in part 

 ha\e seen by direct experiment, the nervous system can influence the 

 work of our glands in the most diverse ways. The vagus nerve, 

 already burdened with many duties, has, in addition, proved itself 

 to be an undoubted exciter of the gastric glands and of the 

 pancreas. But we must also assign to the sympathetic nerve a similar 

 role. This is a matter which cannot be doubted, so far as the pancreas 

 is concerned, and is highly probable as regards the stomach. We also 

 saw good reason for believing that these two nerves contained two 

 different classes of fibres, secretory and trophic, a condition which had 

 already been proved to exist by Hoidenhain for the nerves of the 

 salivary glands. As a hypothesis we might even have proceeded a step 

 farther and have divided Heidenhain's trophic nerves into separate 

 classes of secretory fibres. Lastly, we advanced important experimental 

 evidence to show the existence of special inhibitory fibres to the glands, 



