418 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



certain instances it lias been found to turn acid on standing. As regards 

 its digestive action, it contains three ferments, which may be precipitated 

 by alcohol and again redissolved in water. It will rapidly convert 

 starch into sugar in a neutral or faintly alkaline medium, while 2 per 

 cent, of acid and 5 per cent, of liquor potassa will prevent it. This has 

 also been established by Ellenberger and Hofmeister to apply to the 

 intestinal secretion of the horse. There is a special ferment present 

 which will convert cane-sugar into invert-sugar, or a mixture of laevulose 

 and dextrose. This is the only secretion in the body which possesses 

 this power. The transformation of cane-sugar into invert-sugar is 

 represented in the following formula : 



SC^H^O^ +2H 2 = C 12 H 24 12 + C 12 H 24 O 12 . 

 Saccharose. Water. Dextrose. Lsevulose. 



The inversive ferment has been found by Bernard in the small intes- 

 tine of dogs, rabbits, birds, and frogs. Roberts has recognized it in the 

 small intestine of the pig, the fowl, and the hare, while Balbiani has 

 found it in the intestine of the silk-worm. It is absent from the large 

 intestine. When a watery infusion is made of the mucous membrane of 

 the small intestine, it possesses the power of inverting sugar, but loses it 

 when the infusion is filtered, seeming to indicate that the ferment remains 

 attached in such infusions to some of the formed elements contained in 

 the intestine. It is, however, possible to precipitate the ferment from 

 intestinal juice, and then obtain a watery solution of the precipitate 

 which will invert sugar. The intestinal juices will also dissolve proteids, 

 albumen, and fibrin, and convert them into peptone, after first passing 

 through a stage similar to that of alkali albumen. The action of the 

 intestinal juices resembles that of the pancreatic secretion in its general 

 characters and in the resolution of the fibrin peptone into leucin and 

 tyrosin and indol. The ferment which is concerned in the digestion of pro- 

 teids is apparently either not carried down by the alcohol, or is not capable 

 of resolution in water, for all the author's experiments failed in obtaining 

 an active solution of the ferment in water, acid, or alkali after precipi- 

 tation with alcohol. When fibrin is digested by the intestinal juices, a 

 peculiar substance is formed, which gives a red with nitric acid, the color 

 disappearing on heating. 



IV. FERMENTATION PROCESSES IN THE SMALL INTESTINE. In the 

 small intestine are found numerous examples of the lower organisms 

 which enter the alimentary canal through the foods and liquids which 

 are swallowed, and which induce various fermentations and putre- 

 factions in the contents of the alimentary canal, resulting in the evolu- 

 tion of various gases. These gases consist, in the first place, of air, which 

 is swallowed with the food, of which a large portion of the oxj^gen is 



