Handbook of bacteriology for nurses / [Harry Wardwell Carey].

  • Carey, Harry Wardwell, 1875-1935.
Date:
1930
Catalogue details

Licence: In copyright

Credit: Handbook of bacteriology for nurses / [Harry Wardwell Carey]. Source: Wellcome Collection.

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    tion in the intestine is dependent to a large extent on the breaking down action of bacteria. We cannot ab- sorb meat and vegetable as such, and it is only after our food has been separated into simple compounds and elements that it is absorbed to nourish the body. In this process the bacteria play no small part. But bac- teria are not only agents capable of breaking down complex substances; they also build up substances from chemical elements. Some plants take their nitrogen from the air, but they would not be able to do so were it not for the presence of certain bacteria growing in the roots. The maintenance of life in the world is often de- scribed as a cycle: first, the chemical elements are built up into plants, the plants nourish the animals, then the animal tissue is consumed and excreted to be broken down into elements. In each step the bacteria play a most important part. Commercial Use of Bacteria.—These activities of bacteria and their enzymes are made use of commer- cially; the fermenting action on sugars converting them into alcohol is used in making beer and wine, the clot- ting of milk by bacteria in making cheese, the ferment- ing of cabbage in making sauerkraut. PTOMAINES. It may be well to mention here certain substances that are formed principally in the decomposition of meat and fish by bacteria. They are called ptomaines, and are present in partially decomposed animal and vegetable matter. Some of them are highly poisonous.