The scientific feeding of animals / by O. Kellner. Authorised translation of William Goodwin.

  • Kellner, O. (Oscar Johann), 1851-1911.
Date:
1915 [pref. 1908]
Catalogue details

Licence: In copyright

Credit: The scientific feeding of animals / by O. Kellner. Authorised translation of William Goodwin. Source: Wellcome Collection.

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    proteins was obtained. It was known that this method was not quite correct, for nitrogenous sub¬ stances of a non-protein nature had already been found in different parts of the plant. The amount of these non-protein materials was considered, though, to be so small as to be negligible. The products obtained in this way by calculation from the nitrogen found in the food were called “ crude protein,” or “ nitrogenous substances.” It was not until comparatively recently (1879) that the nitrogenous substances of a non-protein nature were shown to be widely distributed in the plant and animal kingdoms, and to be present in considerable quantities in some food-stuffs. This led to a distinction being made between “ crude protein,” which expresses all the nitrogen-containing compounds, and pure protein,” or, as it is named in some places, “ the proteids.” When making an analysis of a feeding-stuff advantage is taken of the property which proteins possess of combining with metallic salts or tannic acid, whereas non¬ proteins do not. In this way protein can be separated from non-protein and the quantities of each determined. For the analysis the finely- ground food-stuff is treated with warm water, and the substance to be used for precipitation is added. The proteins are in this way precipitated, and the nitrogen can then be determined either in the solu¬ tion which is left after the precipitation, or in the
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