Contributions to the physiology of digestion and to dietetics / by W. G. Aitchison Robertson.

  • Robertson W. G. Aitchison (William George Aitchison)
Date:
1903
Catalogue details

Licence: In copyright

Credit: Contributions to the physiology of digestion and to dietetics / by W. G. Aitchison Robertson. 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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    G21 As regards the order:— the richness of these in starch, the following is Per cent. 1. Tapioca, . 2. Sago, . 3. Arrowroot, 4. Rice, . 5. Macaroni, 6. Barley, 7. Biscuit, 8. Rye, . 9. Flour (wheat), 97 8 86-1 82-4 79-4 76-8 74'3 73-4 73-2 70-3 Method of Investigation. I investigated how far and in what kind of manner salivary digestion proceeded in the various starchy foods after they wei'e cooked and prepared for the table. Ten grammes of each of the various foods were accurately weighed out, placed in a large test-tube, heated to 38° C.; 2 cubic centimetres of mixed human saliva1 (filtered to remove mucus) were added. A series of these tubes was prepared, and the whole was placed on a water-bath kept at a uniform tem- perature of 38° C. At frequent intervals the tubes were well shaken, so as to ensure thorough mixing of the starchy material with the saliva. At intervals of 5, 10, 20, 30, 45, GO, 90, 120, 150, 180 minutes a tube was removed, and the condition of its contents noted. The contents of the tube were then rapidly boiled, to prevent any further amylolytic action of the saliva. The sugar was then extracted by repeated washing with water and filtering. The filtrate was made up to a definite volume and the sugar estimated quantitatively as dextrose, so as to be comparable with the dextrose obtained by boiling the starchy material with dilute acid. Actually, maltose is the sugar pro- duced in greatest amount as a result of salivary proteolysis, and it has a far feebler effect in reducing Teh ling’s solution than has dextrose (the proportion being G5 : 100). For ease in com- parison all the sugar produced has been calculated, however, as dextrose. 1 The collection of saliva was always made in the evening, as Hofbauer has shown that there is great variation in the composition of saliva at different hours of the day (Archiv fiir die gcsammle Physiologie, 1896-7, Bd. 65, p. 503-15).