182 



AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



The digestive power showed a striking increase between the second and 

 third hours. The author gives other tables showing the effect of a meat diet, 

 a milk diet, a bread diet, etc., which seem to show that a meat diet promotes 



the greatest flow of secretion, 

 while the bread diet gives a 

 secretion of more than usual 

 digestive power. 



Khigine attempted to deter- 

 mine the effect of various chemi- 

 cal substances, found in food 

 or occurring during digestion, 

 upon the flow of the secretion, 

 hoping by this means to throw 

 some light upon the nature of 

 the normal stimulus in ordinary 

 gastric digestion. He obtained 

 practically negative results with 

 acids, alkalies, and neutral salts ; 

 none of these substances when 

 introduced into the stomach had 

 any decisive effect upon the se- 

 cretion in the isolated fundus. 

 Water, however, was quite ef- 

 fective; the ingestion of 500 

 cubic centimeters produced a 

 marked and fairly long-con- 

 tinued secretion of gastric juice. 

 But, so far as his experiments 

 went, peptone is, par excellence, 

 the chemical stimulus to the 



FIG. 80. Diagram showing the variation in quantity of 

 gastric secretion in the dog after a mixed meal ; also the 

 variations in acidity and in digestive power (after Khigine). 



gastric glands. The peptones caused an unusual secretion of gastric juice, 

 although the closely related products of digestion known as proteoses (see p. 

 230) had little or no effect. It remains unsettled, however, how the water 

 and the peptones act whether they are absorbed, as Heidenhain thought, and 

 act as chemical stimuli to the glands or the intrinsic ganglia of the stomach, or 

 whether, as Khigine believes, they are direct and as it were specific nerve- 

 stimuli to the sensory nerve-fibres of the mucous membrane, and thus produce 

 a reflex effect upon the efferent secretory nerves to the gastric glands. The 

 latter view would be more in accord with the mechanism of secretion as we 

 know it in the salivary glands and pancreas, but it cannot be said to have 

 been demonstrated as yet. 



Histological Changes in the Gastric Glands during Secretion. The 



s of the gastric glands, especially the so-called chief-cells, show distinct 



changes as the result of prolonged activity. Upon preserved specimens taken 



from dogs fed at intervals of twenty-four hours, Heidenhain found that in the 



