320 PHYSIOLOGY OF ALIMENTATION. 



even show an alkaline reaction in solutions which are really 

 neutral or even acid. 



A number of authors have in recent years employed in- 

 dicators other than litmus (such as lacmoid, phenolphthalein, 

 methyl orange, alkanna, rosolic acid, alizarin, curcuma and 

 trapseolin) to ascertain the reaction of the intestinal con- 

 tents. MuNK, 1 who experimented in this way on dogs and 

 hogs fed on various diets after a period of fasting diets 

 predominantly protein, or protein and fatty, or mixed in 

 character comes to the following conclusions: The con- 

 tents of the duodenum, jejunum, or ileum, in carnivorous as 

 well as in omnivorous animals, no matter how fed, at no time 

 show an alkaline reaction, if only indicators sufficiently sensi- 

 tive to indicate the presence of carbonates and fatty acids be 

 employed. On a pure meat diet the duodenal and upper 

 jejunal contents are distinctly even though only faintly 

 acid. Beyond this point and to the ileocsecal valve the 

 intestinal contents are neither definitely acid nor alkaline, 

 and may, in consequence, be considered neutral. As soon as 

 fat is added to the diet, that is, protein and fat are fed to- 

 gether, the contents of the entire small intestine show an 

 acid reaction, attributable, no doubt, in the main to the 

 presence of free fatty acids formed through the action of 

 lipase upon the neutral fats. In fact, under no circum- 

 stances, even when large amounts of carbohydrates are given 

 together with protein, do the contents of the jejunum or ileum 

 ever show an alkaline reaction. 



The experimental observations of MUNK are corroborated by 

 clinical findings on human beings. MACFADYEN, NENCKI, and 

 SiEBER, 2 who observed two cases of fistula of the ileum just 

 above the ileocaecal valve, found that the contents of the 

 alimentary tract when they passed this point were always 

 acid in reaction when the patients were given a mixed diet. 



1 MUNK: Centralblatt fur Physiologic, 1902, XVI, p. 33. 



2 MACFADYEN, NENCKI, and SIEBER: Archiv fur experimentelle 

 Pathologic und Pharmakobgie, 1891, XXVIII, p. 311. 



