On the digestive ferments and the preparation and use of artificially digested food : being the Lumleian lectures for the year 1880, delivered before the Royal College of Physicians / by Wm. Roberts.

Date:
1880
Catalogue details

Licence: Public Domain Mark

Credit: On the digestive ferments and the preparation and use of artificially digested food : being the Lumleian lectures for the year 1880, delivered before the Royal College of Physicians / by Wm. Roberts. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    becomes a watery liquid. This is evidently a distinct act—and antecedent to the saccharifying process which follows. By operating with small proportions of diastase and large proportions of pm-e starch paste it is possible to hit on a moment when Hquefaction is complete and saccharification is not yet begun. At this moment the solution yields a pure starch reaction, and no reaction of dextrine nor of sugar. The process of saccharification fol- lows immediately on the heels of liquefaction ; and in ordinary manipulations the one process runs into the other. The speed of the action depends primarily on the proportion of the diastase. By adjusting the pro- portions of diastase and starch in such degrees that saccharification will be completed in about a couple of hours, the successive steps of the process can be leisurely followed by applying from time to time the appropriate tests. If you test as soon as liquefaction is complete you get a pure blue with iodine and a slight reaction of sugar with Fehling's solution. In a few minutes the sugar reaction becomes more decided; and, although you stiU get a pure blue with iodine in the ordinary way of testing, you will get, by greatly diluting the blue solution and then adding more iodine, a deep violet tint—showing the presence of erythro-dextrine mixed with starch. The next step is the total disappearance of the blue reaction with iodine, and the substitution for it of an intense red-