Table 15. — The pH of Stomach Contents 



Animal 



pH 



Author 



Man minimum pH 



1.0 to 2..5 

 Eat _. 3.2-4.6 



McClendon and Medes (1925) 

 Kahn and Stokes (1926) 

 Sun, Blumenthal, Slifer, Ber- 

 ber and Wang (1932) 

 Eastman and Miller (1935) 

 Kofoid, McNeil and Cailleau 



(1932) 

 Schwarz, Steinmetzer, and 

 Caithaml (1926) 



McLaughlin (1931) 

 McLaughlin (1931) 

 Maun and Bollman (1930) 

 Schwarz and Danziger (1924) 

 Nagl (1928) 



McLaughlin (1931) 

 Ashcraft (1933) 



McLaughlin (1931) 



Ashcraft (1933) 



Schwarz and Kaplan (1926) 



Mangold (1925) 



Davey (1938) 



Schwarz and Gabriel (1926) 

 Kreipe (1927) 

 Ferber (1928) 



1926; Redman, Willimott, and Wokcs, 1927). The pH may be 

 appreciably lowered by addition of cod liver oil to a rachito- 

 genic diet. The effect of varying the proportions of protein, 

 fat, and carbohydrate has been reported to cause no marked 

 change in the pH of the intestine of rats (Redman, Willimott 

 and Wokes, 1927), dogs (Grayzel and Miller, 1928; Graham and 

 Emery, 1928), or man (Hume, Denis, Silverman, and Irwin, 

 1924). However, the data of Robinson and Duncan (1931) 

 show consistently higher pH values for rats fed on grain and 

 alfalfa than for rats on a high protein diet (Table 16). East 

 man and Miller (1935) studied the effect of a number of diets 

 on gastrointestinal pH in rats. 



It has been suspected for some time that the pH of the cen- 

 tral portion of the lumen is not the same as that close to the 

 intestinal wall. Evidence for this is found in the feces in that 



the surface of stools is more alkaline, apparently because of 

 secretion of alkaline salts by the intestinal wall. Kofoid, Mc- 

 Neil, and Cailleau (1932) reported ditterences in the pH of 

 contents and wall throughout the digestive tract of the rat. (Ta- 

 ble 16). Robinson (1935) studied the effect of placing various 

 salt solutions in the small intestine of dogs on the pH of the 

 solution and decided that each portion of the digestive tract 

 tended to produce a characteristic pH value in the solution, re- 

 gardless of the initial pH. He concluded that the pH of the 

 region close to the wall increases regularly from pH 6.5 to 7.5 

 or 8.0 throughout the length of the small intestine and pointed 

 out that the pH close to the wall is probably largely indepen- 

 dent of changes produced in the lumen by the action of bac- 

 teria. Ball (1939), by means of a capillary glass electrode, has 

 measured the pH of the wall (data given in Table 16). 



The possibility that pH may be a limiting factor in the dis- 

 tribution of sheep nematodes was investigated by Davej' (1938). 

 He found that Ostertagia circumcincta was able to live between 

 pH 3.2 and pH 9.0. This range allows it to live in the aboma- 

 sum of sheep (pH 3.2-5.25) but apparently may be one rea- 

 son why it does not infest the stomach of the dog (pH 2 or 

 less) or horse (pH 1.1-6.8) or the abomasum of cattle (pH 

 2.0 to 4.1). Two duodenal species from sheep, Trichostrongylus 

 cohibriformis and T. vitrii-s. were alilc to stand a continuous 

 acidity as low as pH 3.6, but five other species {Nematodirus 

 fiUcoUis, N. spathiger, Cooperia oncophora, Cooperia curticei, 

 Strongyloides papillosus) from the middle and lower small in- 

 testine were killed at acidities of pH 3.9 to 4.6. Since the duo- 

 denum is more acid than the ileum, the low resistance to acidity 

 may be an important factor in preventing the five species from 

 the middle and lower intestine from infesting the duodenum. 

 It has been suggested by Lapage (1935a, 1938) that pH has an 

 influence on the second ecdysis of triehostrongylid larvae (out- 

 side of the host) and that this may be of importance in allow- 

 ing development of the parasite. The third ecdysis (in the 

 intestine) might be similarly affected. 



It seems possible that the presence of nemas in the digestive 

 tract might cause a change in gastrointestinal pH, either 

 directly (perhaps because of lesions in the epithelium) or in- 

 directly through the systemic reactions of the host. In cases 

 of ancylostomiasis and intestinal schistosomiasis Eldin and 

 Hassan (1933) found evidence of gastric disturbance which 

 disappeared after removal of the worms. Fernandez (1934), 

 however, found no correlation between gastric acidity and hel- 

 minth parasites. 



DISSOLVED SUBSTANCES (EXCLUSIVE OF GASES) 



The dissolved materials of the digestive tract consist of the 

 ingesta and various secretions listed above, the products of 

 digestion, and the products of bacterial decomposition. Many 

 of these, especially the carbohydrates, may serve as food for 

 nematodes; many others may be toxic and may be effective in 



Table 16. — The pH of the digest ive tract contents. 



Animal and Diet Duodenum Jejunum 



Ileum 



Caecum 



Colon 



Investigator 



Man 



Man _ 



Man 



Dog . — 



Dog 



Dog - — 

 Dog — 

 Cat 



2.27-7.8 

 4.7 -6.5 



4.5 

 2.0 

 6.2 

 5.9 



-5.1 

 -7.6 

 -6.5 



Rat 



Eat — grain & alfalfa 



Rat — high protein 



Eat — high base 



Rat 



Eat — lumen of gut . 

 Rat — wall of gut... 



Rat — wall of gut 



Rabbit 



Cattle 



Cattle 



Horse 



6.5 



6.5 



6.75^ 



6.4> 



6.4^ 



5 gi 



(4.2 -6.9) 



6.93 

 6.34 

 7.35 

 6.68 



7.0 



7.0-7.6 

 6.0-7.0 

 6.0-6.27 



to 



7.7' 

 6.8' 

 6.8' 

 6.6' 

 (5.0-7.3) 



8.42 



6.1-7.3 

 5.9-6.5 



6.0-8.0 

 6.0-7.0 

 6.36 



6.8 

 7.2 

 8.2' 

 7.3' 

 7.25' 

 6.9' 



(5.6-7.7) 

 7.13 

 7.34 

 6.89 

 8.0 

 8.2 



Hogs, calves, lambs .. 



Fowl 



Fowl — meat scrap 



Fowl h 20% lactose 



6.72 .... 7.09 



Indefinitely variable 6.48 to 7.76. 

 More often acid than alk. 

 6.3 _. 6.22 



5.96 ._ 7.1 



6.51 .._ 7.16 



6.0-6.5 

 6.57 



6.5-7.2 

 7.0 

 7.3 

 7.0 

 6.4 



(5.1-7.4) 

 7.13 

 7.34 

 7.06 

 6.26 

 8.2 



8712 



7.4 



6.84 

 7.6 ■ 

 5.25 

 6.4 ■ 

 7.2 

 7.2 

 7.2 

 6.6 

 (5.4 ■ 

 7.33 

 6.95 

 6.91 



7.4-8.4 



8.4 

 6.6 



7.5) 



Long and Fenger (1917) 



Karr and Abbott (1935) 



McClendon (1920) 



Mann and Bollman (1930) 



Graham and Emerv (1927-28) 



Grayzel and Miller (1928) 



Heupke (1931) 



McLaughlin (1931) 



Sun, Blumenthal, Slifer, Herber, and Wang ( 1932 ) 



Robinson and Duncan (1931) 



Robinson and Duncan (1931) 



Robinson and Duncan (1931) 



Eastman and Miller (1935) 



Kofoid, McNeil, and Cailleau (1932) 



Kofoid, McNeil, and Cailleau (1932) 



Ball (1939) 



McLaughlin (1931) 



Danniger, Pfragner, and Sehultes (1928) 



Heupke (1931) 



Danniger, Pfragner, and Sehultes (1928) 



Long and Fenger (1917) 



'Intestine divided into three approx. equal portions so that the measurements given may not correspond exactly to those 

 of the duodenum, jejunum, and ileum. 



"Possibly a misprint in the original paper. 



358 



