462 DIGESTION. 



study the influence of psychical moments on one side and the direct action of food 

 on the mucous membrane on the other. After a method suggested by HEIDENHAIN 

 and later improved by PAWLOW and CHIGIN, they have succeeded in preparing 

 a blind sac by partial dissection of the fundus part of the stomach, and the secre- 

 tion processes could be studied in this sac while the digestion in the other parts 

 of the stomach was going on. In this way they were able to study the action of 

 different foods on the secretion. 



The most essential results of the investigations of PAWLOW and his 

 pupils are as follows: Mechanical stimulation of the mucosa does not 

 produce any secretion. Mechanical irritation of the mucous membrane 

 of the mouth causes no reflex excitation of the secretory nerves of the 

 stomach. There are two moments which cause a secretion, namely, 

 the psychical moment the passionate desire for food and the sensa- 

 tion of satisfaction and pleasure on partaking it and the chemical 

 moment, the action of certain chemical substances on the mucous mem- 

 brane of the stomach. The first moment is the most important. The 

 secretion occurring under its influence by the vagus fibers appears earlier 

 than that produced by chemical irritants, but only after an interval of 

 at least 4J minutes. This secretion is more abundant but less contin- 

 uous than the " chemical." It yields a more acid and active juice than 

 the latter. As chemical excitants which cause a secretion reflexively 

 through the stomach mucosa we include water (slight action) and cer- 

 tain unknown extractive substances contained in meat and meat extracts, 

 in impure peptone, and also, it seems, in milk. According to HERZEN 

 and RADZIKOWSKI 1 and others, alcohol is also a strong agent in produc- 

 ing a flow of juice. The claims in regard to the action of sodium chloride 

 and alkali carbonates are somewhat disputed. That the alkali carbonates 

 retard or inhibit secretion is the opinion of many, but from more 

 recent determinations 2 it would seem as if the concentration of the car- 

 bonate as well as of sodium chloride exercises a certain influence, so that 

 a weaker concentration is indifferent or retarding, while somewhat stronger 

 concentration has an accelerating action upon secretion, though inves- 

 tigators are not agreed as to results. Bitter substances partaken of in 

 small amounts a certain time before a meal increase the secretion, while 

 larger amounts have a retarding action (Bomssow, STBASHESKO 3 ). 

 Fats have a retarding action on the appearance of secretion and diminish 

 the quantity of juice secreted as well as the amount of enzyme. The 

 substances, such as egg-albumin, which do not act as chemical stimulants, 



1 Pfliiger's Arch., 84, 513. 



2 See Rozenblatt, Bioch. Zeitschr, 4; Mayeda, ibid., 2; Pimenow, Bioch, Centralbl., 

 6; Lonnquist, Maly's Jahresb., 36. 



3 Borissow, Arch. f. exp. Path. u. Pharm., 61; Strashesko, see Biochem. Centralbl.,, 

 4, 148. 



