Vegetable Albumen^ Fat and Starch. 421 



dryness in the water-bath, and treated with alcohol and oxide 

 of zinc with the necessary precautions; prismatic crystals were 

 obtained corresponding with lactate of zinc, but in too minute 

 quantity to admit of analysis, the only demonstrative argument. 

 The preceding experiments appear to show, however, that 

 the free acid of the stomach, in the digestion of vegetable 

 matter at least, of all the known acids, alone corresponds with 

 the lactic. To determine the nature of the volatile acid, which 

 however appears to be present always in minute quantity, a 

 portion of gastric fluid was distilled, and the product was ob- 

 tained in three distinct receivers. Their characters, as deter- 

 mined by infusion of litmus, were as follows : — 



1 St prod UCt of distillation Infusion of litmus. 



amounted to ... 1 oz., bright red colour, 



2nd ... ... li oz., paler than preceding. 



3rd ... ... 1 oz., slight red colour. 



From these observations, it would therefore appear that the 

 greatest amount of volatile acid was carried over at first, and 

 that as the distillation proceeded its amount in the retort 

 gradually diminished, indicating that the acidity was not due 

 to the decomposition of lactic acid or its eduction by the vapour, 

 but rather to the presence of acetic acid. The quantity pre- 

 sent was however trifling, since the distilled product of a large 

 amount of gastric fluid could never be detected in a state of 

 effervescence on the addition of carbonate of soda. 



Dext7'in and Soluble Starch found in the Stomach in the Di- 

 gestion of Starch, — I have already stated in a previous part of 

 this paper that I was unable to detect any traces of starch in 

 the serum of the blood. It was therefore necessary to return 

 to the stomach, and to observe the chemical changes to which 

 the starch was subjected in that viscus. When an animal is 

 fed on porridge, if water be added to the contents of the 

 stomach, the mixture well-stirred and then allowed to stand 

 at rest, the supernatant liquor produces a blue colour with 

 tincture of iodine; but if the liquid be filtered, the colour 

 obtained by mixing the solution of iodine with the filtered 

 liquor is red, indicative of the presence of dextrin, or one of 

 the varieties of soluble starch. I have sometimes found, how- 

 ever, that starch has existed in solution in the gastric fluid 

 even when neither a blue nor a red colour was indicated by 

 iodine. This substance 1 have isolated by boiling the gastric 

 fluid in order to coagulate the albumen, evaporating to dry- 

 ness in the water-bath, and then removing the sugar and oil 

 by means of alcohol. The substance thus obtained gave no 

 decided indications with tincture of iodine previous to isola- 



