CG THE WORK OF THE DIGESTIVE GLANDS. 



submitted to separate and careful observation. To me it appears that 

 the unjustified analogy drawn between the abdominal and salivary 

 glands has to be credited with another important misapprehension. 

 And precisely for this reason I think it desirable to bring under 

 consideration, if only in brief fashion, the conditions of work of 

 the salivary glands, especially since Dr. Glinski has instituted in the 

 laboratory some easily performed experiments which bear upon the 

 matter. 



The experiences of daily life teach us from the outset, that the 

 activity of the salivary glands begins even before the introduction of 

 food into the mouth. With an empty stomach, the sight of food or 

 even the thought of it is sufficient to set the salivary glands at once 

 into activity ; indeed, the well-known expression, " to make one's mouth 

 water," is based upon this fact. Hence a psychic event, the eager 

 longing for food, must be accepted as an undoubted excitant of the 

 nervous centre for the salivary glands. On the other hand, the same 

 everyday experience, as well as numerous experiments upon animals, 

 teach us that a number of substances, when brought into contact 

 with the mucous membrane of the mouth, are likewise able to call 

 forth a secretion of saliva. One even acquires the impression that 

 everything brought into the mouth may reflexly influence these 

 glands, the only difference being a gradual shading off' in the effect, 

 dependent upon the strength of the stimulation which the substance 

 introduced is able to exert, and it appears to me that it is precisely this 

 impression which has driven the idea into the background, that the 

 peripheral end-apparatus of the centripetal nerves of the digestive canal 

 are specifically excitable. The facts were here correctly observed, but 

 their indications erroneously interpreted. 



The great multiplicity of excitants of salivary secretion, has without 

 doubt, some connection with the complicated physiological functions of 

 the saliva. This is the first fluid encountered by everything which 

 enters the alimentary canal. It must, therefore, in a sense play the 

 part of host to every substance taken in moisten the dry, dissolve the 

 soluble, envelop the hard and bulky with mucus in order to facili- 

 tate its passage down the narrow oesophagus ; and submit certain forms 

 of food material, such as starch, to a process of chemical elaboration. 

 Nor is its duty by any means ended here. The saliva is secreted in the 

 first compartment of the alimentary canal, which is at the same time 

 the sorting-room of the organism. Much of what enters the mouth 

 may prove in the testing process to be useless, or even noxious, and 

 must either have its deleterious properties neutralised or be com- 

 pletely rejected. The saliva is secreted in the first instance to obviate 

 injurious effects in some way; thus, for example, a strong acid is to 



