THE WORK OF THE SALIVARY GLANDS APPETITE. <i!> 



effect of large pieces of flesh is naturally much greater than that of 

 the finely powdered material, and yet it was precisely to the latter 

 that the glands responded. The stimulus is, therefore, not due to the 

 mechanical, but to some other property of the food. This other property 

 is obviously the dryness of the material. Our example illustrates how 

 that which we may term "purposiveness" comes into play in the working 

 of our glands and albo how erroneous is the opinion that the me- 

 chanical stimulus is all potent. Indeed, previous authors have already 

 pointed out that dry substances cause a specially free secretion of saliva, 

 and yet physiological opinion throughout the length and breadth of the 

 land, as expressed in text- books, has chosen to recognise a universal 

 instead of a specific excitability. Dr. Wulfson, who is at present carry- 

 ing on the investigation of salivary secretion in our laboratory, has added 

 a very interesting observation to the results of Dr. Glinski already 

 related. The parotid gland, which is hardly, if at all, excited when one 

 offers fresh meat to the animal, responds with a very active secretion, 

 when dry food (bread or powdered meat) is offered. This phenomenon 

 is all the more surprising since the desire of the animal for eating is 

 much more strongly excited by flesh than by dry bread. I am quite 

 convinced that an exact study of the exciting agencies of the three 

 salivary glands will furnish a number of new data bearing upon the 

 question in hand. 



The second reagent which is poured out on the raw material in the 

 digestive canal is the gastric juice. How, in the normal course of 

 events, is the work of the gastric glands, which prepare this juice, called 

 into play ? With the first, and manifestly important factor, which has 

 a relation thereto, you are already acquainted, and, indeed, have already 

 seen. I refer to the production of gastric juice in the empty stomach, 

 as a result merely of the swallowing of food in the so-called sham 

 feeding of an oasophagotomised dog. When one takes into considera- 

 tion the absolute independence of this factor, and the intensity of the 

 effect, which makes itself evident in the secretion of a large quantity of 

 juice of high digestive power, the exciting agency which brings about 

 such secretion must be recognised as one of the most important and 

 effective processes in gastric digestion. But in what does it consist ? 

 At first sight it appears and when I previously drew your attention to 

 the fact I expressed the opinion that there is here a simple reflex effect 

 from the cavity of the mouth upon the secretory nerves of the stomach, 

 similar to the reflex excitation, e.y., of the parotid gland, by finely 

 powdered flesh thrown into the mouth. Now, however, I assert quite 

 emphatically that this is not the case. We have, it is true, in the 

 activity of the salivary glands an analogous phenomenon to indicate 

 not, however, that of which we have just spoken. \Ve might apply 



