CHAP. II.] LACTIC AND BUTYRIC ACIDS. 99 



to 40 C., it possesses no digestive properties. These experiments 

 appear to negative conclusively the hypothesis that the hydrochloric 

 acid of the gastric juice exists hi' combination with leucine. 



The progress of research will probably shew that the deviation 

 from strict normality exhibited by the hydrochloric acid of the gastric 

 juice is due to the organic matters which it contains. Nevertheless 

 the information obtained by Richet on the main question viz. that 

 the acid of the fresh gastric juice is essentially one, and that it 

 behaves to ether as a mineral acid, must be considered as having 

 added very greatly to our knowledge of the gastric juice, and taken 

 in connexion with other facts also discovered by him, to our know- 

 ledge of gastric digestion. 



Lactic and Butyric Acids in the Gastric Juice. 



Although the evidence afforded by various colouring matters 

 supports that furnished by other methods of research and leads us 

 to conclude that the essential acid of the gastric juice is hydrochloric 

 acid, there can yet be no doubt that the juice obtained during the 

 processes of digestion contains other acids and especially lactic, 

 butyric and acetic acids, together frequently with free vegetable 

 acids such as malic, the result of the decomposition of salts contained 

 in the food. Of these acids lactic acid is probably a constant physio- 

 logical constituent of the juice. 



determining ^ n or( ^ er to test for lactic acid in gastric juice, the 



presence of fluid should be repeatedly shaken with ether, and the 

 lactic acid in ethereal solutions allowed to evaporate spontaneously, 

 gastric juice. t ^ e res id ue being dissolved in water and subjected to 

 the following tests : 



1. A dilute solution of ferric chloride is made by adding from 2 

 to 5 drops of a 10 per cent, solution to 50 c.c. of water. Such a 

 dilute solution is almost colourless, possessing only, when examined in 

 thin layers, a very faint straw colour. When a trace of free lactic 

 acid is added to it however, the colour is at once changed to a much 

 deeper yellow-straw colour, a result which is not produced by either 

 hydrochloric, acetic or butyric acids. 



2. Dilute a 4 per cent, solution of carbolic acid with twice its 

 volume of distilled water and add to it a few drops of a solution of 

 ferric chloride, which will give rise to a violet colour. When a 

 solution containing a trace of lactic acid is added to a small quantity 

 of this violet coloured solution, the colour disappears or rather the 

 violet is changed to a yellow colour (Urfelmann's Reaction 1 ). This 

 reaction is inferior in value to the first mentioned. 



1 Uffelmann, Deutsches Archiv fiir klin. Med. Vol. xxiv. (1884), p. 437. 



72 



