A manual of hygiene and sanitation / by Seneca Egbert.

  • Egbert, Seneca, 1863-1939.
Date:
1898
Catalogue details

Licence: Public Domain Mark

Credit: A manual of hygiene and sanitation / by Seneca Egbert. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    the class are beneficent in many others. For example, they enable those plants, the leguminosse, which yield ns the largest supply of vegetable proteids, to derive much of their nitrogen almost directly from the atmosphere; they have much to do with the flavor and value of dairy products, and new uses in which they may be employed in the domestic or commercial affairs of life are being announced from day to day. And thus we find this class of the bacteria, which comprises by far the greater number of species, to be our benefactors and indispensable servants both in preventing the accumulation of noxious and harm- ful substances upon the earth and in really helping to produce the food which we eat. The parasitic bacteria, on the other hand, have their habitat in or upon highly organized living matter, and exist at its expense. They also produce in their growth substances called toxins, that are either locally or generally poisonous or harmful to the organism that is their host. It is needless to say that it is in this class that we find the disease germs, or pathogens, as some would call them. It should not be forgotten, however, that the saprophytes, in the decomposition of complex organic bodies, may also produce ptomaines, more or less toxic to animal life. Of these latter we may instance as good examples the dan- gerous tyrotoxicon, a by no means uncommon product in the decomposition of milk, ice-cream, etc., the cadaveric poisoning of the dissecting-room, etc. But, while these ptomaines are more or less characteristic of the respective bacteria that produce them, each varies in its composition and properties according to the substance upon or in which it is produced. We say that an organism is optional when it is at one time a saprophyte and at another a parasite, or at one time