Recent advances in the physiology of digestion.

  • Starling, Ernest Henry, 1866-1927.
Date:
1906
Catalogue details

Licence: In copyright

Credit: Recent advances in the physiology of digestion. Source: Wellcome Collection.

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

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    reduced in the alimentary canal or in its walls to the form of monosaccharides. As regards proteids, the processes of digestion have a different significance according as we are dealing with their value as givers of energy or their value as builders up of the living protoplasm. If the proteids of the food are to be oxidised and utilised as a source of energy, it is only necessary to render them soluble so as to assist their absorption. If, however, they are to be built up as integral parts of the living cells, to take the place of molecules which have been destroyed in the wear and tear of the processes of life, a much more profound change is necessary. The proteids of the cells from different parts of the body have different molecular constitutions. Not only do they differ among themselves, but they differ very largely from many of the proteids which may be taken in with the food. A child is able to obtain material for the growth of his brain cells, his muscle cells, his liver cells, from a diet containing proteid in the form of caseinogen, of vegetable gluten, of meat fibrin, or vegetable proteid, such as edesthi. A reference to the following tables will show the striking difference in com- position between the various proteids of the food and the proteids which have to be formed from them in the living tissues. We may take for example the manner in which the nitrogen is combined in the different proteids. For purposes of classi- fication the nitrogen can be divided into three fractions, accord- ing to its behaviour in the product of the acid hydrolysis of the proteid. These fractions are— (a) The portion which is driven off as ammonia by heating the acid mixture with alkalies or magnesia, the so-called ammonia- or amide-nitrogen; (6) That contained in the form of monoamino-acids; (c) That contained as diamino-acids, or as bases such as