BACTERIAL DIGESTION IN THE INTESTINE 539 



that animals can be rendered immune to this proteose by progressively 

 increasing periodic administration. When they are thus immunized, 

 the toxic symptoms do not follow upon its injection, nor are the symp- 

 toms produced by artificially creating an intestinal obstruction. Con- 

 versely, when a chronic toxic condition is kept up by a partial obstruc- 

 tion, such as that produced by making a gastrojejunal fistula and occlud- 

 ing the duodenum, the animals are less susceptible than normal ones to 

 proteose injection. 



We have here and there incidentally referred to the reaction of various 

 parts of the gastrointestinal contents, but we would call attention once 

 again to this important subject, especially since many points of uncer- 

 tainty have recently been cleared up by the accurate observations of 

 Long and Fenger, 29 who used the electrometric method for measuring 

 the hydrogen-ion concentration. The contents of the duodenum removed 

 by means of the Eehfuss tube in man showed a reaction varying from dis- 

 tinctly acid to slightly acid, depending upon the proximity of the tube 

 to the pylorus or papilla, this position being determined by x-ray exam- 

 ination. The slight degree of alkalinity is surprising. Lower down in 

 the duodenum the reaction was as frequently acid as alkaline, the de- 

 gree of acidity, however, being so slight as to favor rather than retard 

 the digestive powers of the pancreatic juice. 



To determine the reaction lower down, the observations were made on 

 recently slaughtered animals (pigs, calves, and lambs), the small intes- 

 tine being tied off in loops of the upper, middle, and lower thirds. The 

 contents of the last loop were often alkaline, but might be more acid even 

 than those of the first, which were usually faintly of this reaction. Con- 

 siderable variations were, however, the rule. The mixed intestinal con- 

 tents of a recently fed dog, removed immediately after death, gave 

 P H = 6.79 ; i. e., very faintly acid. 



DIGESTION REFERENCES 

 (Monographs) 



iPavlov, J. P.: The Work of the Digestive Glands. Trans, by Sir W. H. Thomp- 

 son, London, Griffin, ed. 2, 1910. 



2Starling, E. H. : Recent Advances in the Physiology of Digestion, W. T. Keene & 

 Co., Chicago, 1907. 



sCannon, W. B.: The Mechanical Factors of Digestion, Internat. Med. Monographs, 

 London, Ed. Arnold, 1911. 



^Carlson, A. J.: The Control of Hunger in Health and Disease, Univ. of Chicago 

 Press, 1917. 



sTodd, T. Wingate: The Clinical Anatomy of the Gastrointestinal Tract, Manches- 

 ter, Univ. Press, 1915. 



eMacallum, A. B.: Ergeb. der Physiol., xi, 598-657. 



'Cannon, W. B., and Cattell, McKeen: Am. Jour. Physiol., 1916, xli, 39. 

 E.: Proc. Am. Physiol. Soc., Am. Jour. Physiol., 1918, xlv, 559. 



