38 THE WORK OF THE DIGESTIVE GLANDS. 



is distributed, however, over a much longer time, so that the mean 

 hourly quantity of juice with bread diet is one and a half times less 

 than after taking milk or flesh. Consequently, in the digestion of 

 bread, but little hydrochloric acid is present in the stomach during 

 the whole period of secretion. This harmonises well with the 

 physiological-chemical observation that the digestion of starch, which 

 is contained in large quantities in bread, is impeded by an excess of 

 acid. From clinical observations we know further that, in cases of 

 hyperacidity, a large part of the starch of bread escapes unused from 

 the gastro-intestinal canal, while flesh is excellently digested. 



Towards aiding the digestion of starch, or at all events with 

 relation thereto, another phenomenon also plays a part which has already 

 been several times mentioned but not yet explained. I mean the long 

 pause of at least five minutes' duration which always intervenes between 

 the taking of food and the beginning of secretion. This interval 

 always occurs, whether the observation be made on the complete 

 stomach with the aid of sham feeding, or on the miniature stomach of 

 a dog normally fed. 



This latent period, as it may be termed, is never less than four and 

 a half to five minutes, but may often be as long as ten minutes. 

 What is its significance ? We have no reason for interpreting its 

 occurrence on the basis of extrinsic conditions, to wit, such time as 

 might be supposed to be necessary for the glands to fill up to their 

 mouths, or till the juice moistens the inner wall of the stomach and 

 runs in streamlets towards the fistular orifice. This cannot be the 

 explanation, since the latent period occurs when the glands are 

 already filled with juice, and the secretion spreads out over the 

 gastric wall. Further, it would be singular to suppose that the gastric 

 glands per se, are incapable of responding to a stimulus before the lapse 

 of five minutes after its application. Nothing, therefore, remains but to 

 recognise in the occurrence of the latent period a definite aim. Perhaps 

 these five to ten minutes are reckoned upon to allow the action of the 

 amylolytic ferment of the saliva to proceed. But this explanation 

 cannot, of course, be regarded as very convincing, so long as the 

 question has not been systematically brought under the scrutiny of 

 scientific investigation. 



All the more gladly do I now proceed to the work of the pancreatic 

 gland, since here the adaptation of the secretion to the nature of the 

 requirements is beyond all doubt. In the following table the experi- 

 ments of Dr. Walther are collected together, which illustrate the work 

 of the pancreatic gland upon different diets : 



