92 c. SCHMIDT'S RESEARCHES ON ACID OF GASTRIC JUICE. [BOOK n. 



Thomson 1 , came to the same conclusion as Lehmann, and opinions 

 were much divided as to the causes of the acidity of the gastric juice 

 until the researches of C. Schmidt about to be referred to. 



c. Schmidt's As a result of eighteen concordant analyses of the 

 gastric juice of carnivorous animals, Bidder and Schmidt 

 announced in 1852 that the gastric juice of animals which have pre- 

 viously fasted for a period of 18 20 hours contains only free hydro- 

 chloric acid and no trace of lactic acid or of any other organic acid. 

 The gastric juice of herbivorous animals was however found to contain 

 small but variable quantities of lactic acid, doubtless derived from 

 the starchy constituents. 



The method followed by C. Schmidt consisted in precipitating a 

 weighted quantity (100 grammes) of gastric juice, which had been 

 strongly acidified by nitric acid, with silver nitrate. The silver 

 chloride thus precipitated was after suitable treatment weighed, and 

 furnished the total amount of chlorine present either as hydrochloric 

 acid or in combination with bases. The nitrate was then freed from 

 silver by the addition of an excess of hydrochloric acid, evaporated to 

 dryness, ignited, and the total amount of bases present determined. 



It was found that in every case the amount of Cl present was 

 larger than could have been the case had the whole of the bases been 

 present as chlorides. Further, the amount of free acid present was 

 determined by neutralizing with weighed quantities of solutions of 

 caustic potash, as well as of lime and baryta water, and it was found 

 that the amount of base required for neutralization corresponded to 

 the amount of hydrochloric acid determined by the first method 

 of research, whilst had lactic acid been present, a larger quantity 

 of alkali would have been needed for neutralization 2 . 



Since these investigations of C. Schmidt it has been admitted that 

 the cause of the acidity of the normal gastric juice is hydrochloric 

 acid, though, as will be shewn in the sequel, Richet has of late 

 advanced the view that the acid is conjugated with an organic 

 body, presumably leucin. 



Certain Colour Reactions depending upon the nature of the 

 Acid of the Gastric Juice. 



Various colour reactions have been discovered of late years, which 

 enable us to discriminate between dilute solutions of mineral and of 

 organic acids; these have been applied to the investigation of the 

 gastric juice with the result of confirming the observations of Prout 

 and of C. Schmidt, and of proving that the healthy gastric juice con- 

 tains a free mineral acid and therefore hydrochloric acid. 



1 Thomson, London, Edin. and Dublin Philosoph. Mag., 1845. 



2 Bidder u. Schmidt, Die Verdauungssdfte und der Stqffwechsel, page 44 et seq. 



