Volume 1

A Textbook of the theory and practice of medicine ... / edited by William Pepper.

Date:
1893-94
Catalogue details

Licence: Public Domain Mark

Credit: A Textbook of the theory and practice of medicine ... / edited by William Pepper. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    bacteria from diarbohydrates, the alcoholic, the lactic acid, the butyric acid, the various slimy, viscous, or mucic fermentations, and the fermentation of cellu- lose with production of marsh gas ; the fermentations of the alcohols, of which the most important is the acetic-acid fermentation of ethyl alcohol; the fermentations of the fatty acids; the fermentations converting milk into koumyss. Each species of the zymogenic bacteria is endowed with the power of set- ting up its own special Jiind of fermentation, although a single species may be capable of causing different fermentations, or the same variety of fermenta- tion may be produced by a number of species, or in some fermentations two or more species may be concerned simultaneously or consecutively. These fermentations are intimately associated with the vital processes of the organ- isms producing them, although it is not known in what way, and they cannot be carried to completion by any soluble ferments which have been isolated from the organisms. Soluble ferments, called enzymes, are, however, produced by bacteria, and doubtless play an important role in the metabolism of these lowly organisms as well as in the higher plants and animals. The chemical action of these unor- ganized fertnents is mainly hydrolytic, and does not bring about such compli- cated changes as do the living bacteria in setting up fermentations. Some of these unorganized ferments have been isolated from cultures of bacteria. Bac- teria are capable of producing enzymes with the properties of diastase, of invertin, of pepsin and trypsin, of rennet, of forming ammonium carbonate from urea, and probably also ferments capable of rendering cellulose soluble and of breaking up neutral fats into fatty acids and glycerin. The liquefac- tion of gelatin, which forms one of the distinguishing cultural characteristics of many bacteria, is a process of peptonization by peptic and tryptic ferments, which, indeed, have been isolated, although not in a pure state, from bacterial cells. The products of putrefaction are known only in part, but even the known products are very numerous. The simplest end-products of putrefaction are carbon dioxide, water, hydrogen, nitrogen, and ammonia, to which may be added nitrites and nitrates and the gases, sulphuretted hydrogen, phos- phoretted hydrogen, and marsh gas. But before the end-products are reached a host of intermediary substances are formed. Among these transitional putre- factive products may be enumerated the following : peptones and other proteid substances; nitrogenous alkaloidal bases called ptomains or cadaveric alka- loids, as collidin, neuridin, neurin, cholin, cadaverin, putrescin, spermin, saprin, gadinin, peptotoxin, mydatoxin, mydin, methyl-guanidin, trimethyl- amin and other amines ; other nitrogenous substances, as leucin, tyrosin, taurin, glycocoll; methylmercaptan; tryptophan; aromatic substances, as phenol, indol, skatol, hydroquinon; and organic acids, as formic, acetic, butyric, lactic, propionic, palmitic, caproic, succinic. Processes of hydration, dehy- dration, oxidation, and reduction are concerned in the formation of putrefac- tive products.