Pathogenic micro-organisms : including bacteria and Protozoa; a practical manual for students, physicians and health officers / by William Hallock Park ; assisted by Anna W. Williams.
- William Hallock Park
- Date:
- 1908
Licence: In copyright
Credit: Pathogenic micro-organisms : including bacteria and Protozoa; a practical manual for students, physicians and health officers / by William Hallock Park ; assisted by Anna W. Williams. Source: Wellcome Collection.
21/712 page 3
![put forward in tlieir sup]X)rt Avere so logical and convincing, tliat they continued to gain gronnd, in spite of considerable opposition and ridicnle, and in many instances the conclusions reached have since been proved to he correct. The fact that infectious diseases were of sudden occurrence, breaking ont often in isolated places, and that they frequently remained clinging for long periods to certain locali- ties, leaving other areas unaffected, was evidence that they Avere not produced by a gaseous infective agent. Moreover, the mode of infec- tion, its unlimited development among large numbers of individuals, aud gradiial spread over Avide areas—^the incubation, course of, and resulting immunity in recoA^ery from infectious diseases—all pointed to a living organism as the probable cause. Among other distinguished men of the day A\diose observations exerted a most poAverful influence npon the doctrine of infection may he mentioned Henle. Tlis Avritings {Pathological Investigations, 18T0, and Text-hooh of Rational Pathology, 1853), in which he described the relation of microorganisms to infectious diseases, and defined the character and action of bacteria npon certain phases and symptoms of these affections, are remarkable for their clearness and precision. But, meauAvhile, the question Avhich most interested these investi- gators into the cause of infectious diseases Avas: IVlience are these microorganisms derived Avhich Avere supposed to produce them ? Were they the result of spontaneous generation due to vegetative changes in the substances in Avhich the organisms Avere found, or Avere they reproduced from similar preexisting organisms—the so- called vitalistic theory ? This question is intimately connected Avith the investigations into the origan and nature of fermentation and putrefaction. Spallanzani in 1769 demonstrated that if putrescible infusions of organic matter Avere placed in hermetically sealed flasks and then boiled the liquids Avere sterilized; neither Avere living organisms found in the solutions, nor did they decompose; and the infusions remained unchanged for an indefinite period. The ohjectifm Avas raised to these experiments that the high tem- perature to Avliicli the liquids had been subjected so altered them that S|xmtaneous generation could no longer take place. S]>alhtnzani met tlie objection l>y cracking one of the flasks and alloAving air to enter, Avhen living organisms and decomposition again a]q3eared in the boiled infusions. Another olqcction raised by tlie believers in symntaneous generation Avas that in excluding the oxygen of the air by hermetically sealing the flasks the e.s.sential condition for the development of fermentatioiq Avhicli required free admission of this gas, Avas interfered Avith. This objection Avas then met by Schulze, in 1836, by causing the air admitted to the boiled decomposable liquids to pass through strong sul])huric acid. Air thus robbed of its living organisms did not pro- duce decom|K)sition; Avhercas when no such precautions Avere taken](https://iiif.wellcomecollection.org/image/b28137541_0021.jp2/full/800%2C/0/default.jpg)
