Animal nutrition / [Thomas Barlow Wood].

  • Wood, T. B. (Thomas Barlow), 1869-1929
Date:
1924
Catalogue details

Licence: In copyright

Credit: Animal nutrition / [Thomas Barlow Wood]. Source: Wellcome Collection.

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    liquor pancreaticus, a preparation of pancreatic juice which is made in large quantities for medicinal purposes. Before adding the liquor pancreaticus put a number of spots of iodine solution on a white tile or a piece of glazed paper, and to the first spot add a drop of the starch solution by means of a glass rod. Note the characteristic blue colour. Immediately after adding the liquor pancreaticus, stir with a glass rod and transfer a drop of the mixture to a second spot of iodine. Probably the blue colour will still appear. Repeat this test every few seconds. Very soon no blue colour will be formed. Record the time which has elapsed since the liquor pancreaticus was added up to the point when the mixture first failed to give any blue colour with iodine. Let us suppose that this time was 95 seconds, then 1 c.c. of liquor pancreaticus changes all the starch in 20 c.c. of starch solution kept at 40° C. in 95 seconds. If the time taken was much less than this, repeat the experi¬ ment, using liquor pancreaticus which has been diluted by mixing with several times its volume of water. Repeat the experiment exactly as before, but boil the liquor pancreaticus before adding it to the starch solution. Repeat the experiment as before, but add to the mixture of starch solution and liquor pancreaticus 1 c.c. of dilute hydrochloric acid, and in another case 1 c.c. of dilute sodium carbonate solution. Note that the boiled liquor pancreaticus has no effect on the starch, that dilute hydro¬ chloric acid prevents or greatly delays, whilst dilute alkaline solution of sodium carbonate quickens the rate of change of starch by liquor pancreaticus. Finally, repeat the original experiment, but place the test-tube in cold water, which will be at 12° to 15° C., instead of 40° C. Note that the starch is changed slowly at the lower temperature. Take one of the test-tubes in which the starch has lost all power of giving a colour with iodine, add a little Fehling’s solution, and boil. The blue colour will disappear and a red