The natural history of infectious diseases / by T.W. Thompson.

  • Thompson, T. W. (Thomas William), -1896.
Date:
[between 1892 and 1900]
Catalogue details

Licence: In copyright

Credit: The natural history of infectious diseases / by T.W. Thompson. Source: Wellcome Collection.

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    fore, may have been the origin of life, the conclusion seems forced upon us alike by observation and experiment, that in the present day there is no life in the sense of anything 'which could with any propriety be described as a living being or organism which has not descended from antecedent life. How far this conclusion negatives the possibility of a de novo origin of disease as disease will he presently seen. For it has to be noted that epidemic diseases, as we observe them, are simply the manifestations exhibited by man or other animal of the operation of certain poisons which we assume to be bound up with micro-organisms. And conditions may easily be imagined which would give rise to an apparent or even a real de novo origin of disease independently of any de novo origin of bacteria. To summarise the point reached : We have inferred, provisionally, from what we already know of certain of these diseases, as well as from the general direction of bacteriological research, that all the diseases under con- sideration are due to microphytic life processes ; and we have further seen no reason to doubt that the microphytes upon which these diseases depend are invariably descended from parent microphytes, and that, therefore, nothing of the nature of a true de novo origin occurs so far as the micro- phytes themselves are concerned. Having now sufficiently cleared the ground by a review of the theory of de novo origin of the germs of disease, we may go on to consider the thesis which, in the absence of ‘ spontaneous generation ’ of disease germs, has been regarded by some as the only alternative—namely, the unbroken continuity of disease descent from antecedent cases. This doctrine, signify- ing, as it seems to do, belief that every single case of each of the diseases in question is the progeny, so to speak, of an antecedent case of the same disease, is one of little elasticity. In so far, indeed, as certain of these diseases affect the lower animals as well as man, the antecedent case of a given sample of such disease need not be a human case ; but as regards others, which are held to exclusively affect man, the antecedent case must be sought in the human subject alone. But we now see difficulties in the way of this thesis, and hence arises occasion for reconsideration of the subject from the point of view which regards the microphytes upon which these diseases depend as invariably descended from parent microphytes. Although it is no doubt true that some of the disease microphytes now in question, though capable (whether as bacteria or as spores) of existing in a latent condition outside the body for considerable periods of time, may yet be incapable of passing through their life cycle, including of course pro- liferation, except in human living tissue—so that diseases due to such microbes usually arise (in the present) by direct or indirect infection from a previous human case of the same disease—we nevertheless know that there are microphytes, causative of disease, which are capable of thriving and multiply- ing either upon human or other animal tissues ; and that there are others again which have their habitat largely outside the living body, either human or animal, and are capable of thriving and multiplying upon non-living organic matter. Accordingly, to affirm the continuity of life, from generation to generation, of the microphytic causes of disease, is by no means the same thing as to allege that human diseases descend in a continuous series from human case to human case. For instance, with respect to a particular species of pathogenic micro- organism capable of preying either upon human and other animal hosts, and of thus giving rise to a disease intercommunicable between man and other animals, it is obvious that although the micro-organisms them-