C8 THE WORK OF THE DIGESTIVE GLANDS. 



In his first animal the ducts of the submaxillary gland were thus led 

 outwards. By means of a Mendeljeff's clip, the wide end of a conical 

 funnel of waterproof material was attached to the skin surrounding 

 the orifice. To the narrow end a small test-tube, which served to 

 collect the saliva, was attached by a wire. I now offer such an animal 

 a piece of flesh, and, as you see, the tube fills up at once with saliva. 

 I stop tempting the dog, hang on a new test-tube, and give it a few 

 pieces of flesh to eat ; once more a strong secretion of saliva results. A 

 new tube is now attached to the funnel, the dog's mouth is opened 

 and a pinch of fine sand thrown in; again there is a flow of saliva. 

 Once more a new test-tube ; and now I apply to the buccal mucous 

 membrane, the plume of a feather dipped in acid solution, with the 

 result that I obtain a strong flow of saliva. One may employ a 

 number of substances in this way, when a similar eft'ect is always 

 produced. You see in this, such a comprehensive excitability of the 

 innei vation apparatus of the salivary glands that you might readily 

 interpret it as meaning the power of response to all and sundry forms of 

 stimulation. We now proceed, however, to another dog, whose parotid 

 duct has in a similar manner been diverted outwards. The saliva is 

 collected in the same way. We tempt the dog with a piece of flesh, 

 but to our astonishment no f-aliva flows, and yet the animal is most 

 eager for the savoury meal offered. Now we give it some raw flesh 

 to eat ; again the secretion of saliva is as good as absent ; only when I 

 come near can I detect one or two drops of saliva running down the sides 

 of the tube. Probably ) ou will say there is something wrong, either 

 with the method or with the glands of the animal. But wait a little. I 

 now give the dog finely powdered dry flesh, and obtain at once an abun- 

 dant secretion. Should any one happen to think that the variation 

 in the result is dependent, not on a different specific activity of the 

 glands, but on individual differences in the dogs, I respond that Dr. 

 Glinski has had an animal with double parotid and submaxillary fistula?, 

 and was able to observe on one and the same dog, a like behaviour on 

 the part of the glands to that which Ave have just seen in two different 

 individuals. An analogous experiment with bread was also carried out 

 by Dr. Glinski. The eating of fresh moist bread produced no secretion 

 worth mentioning, while dry bread, on the other hand, caused the saliva 

 to flow in large quantities. The results of this experiment permit us to 

 draw extremely instructive conclusions. In the first place, the several 

 salivary glands are, as a matter of fact, very sharply differentiated in the 

 conditions necessary for their activity that is to say, in respect to the 

 agencies which excite their nervous mechanisms. Secondly, the inner- 

 vation apparatus of the parotid manifests a very sharp selective power 

 in the choice, so to speak, of an adequate stimulus. The mechanical 



