Volume 1

A treatise on hygiene and public health / edited by Alfred H. Buck.

Date:
1885
Catalogue details

Licence: Public Domain Mark

Credit: A treatise on hygiene and public health / edited by Alfred H. Buck. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    27/810 (page 15)
    forming the class of parasitic diseases. Following the usual modern classification, we may divide the infective diseases into: A. Parasitic diseases. B. Contagium diseases. C. Miasmatico-contagium diseases. D. Miasmatic diseases. That the cause of each of the three first classes is specific is inferred from the fact that the disease transmitted is always the same disease. Trichinae never produce hydatids; the bacillus anthracis communicates only splenic fever; small-pox never changes into measles, nor cholera into yellow fever. There is no satisfactory evidence that any of these causes ever arise spontaneously; in every case the pre-existence of the specific poison or organism is necessary. In the majority of parasitic diseases we can recognize the causal organ- ism apart from the disease which it produces, but this is not the case with the other classes; in fact, as soon as we learn clearly the nature and life-habits of an organism causing disease and its mode of propagation, whether within or without the body, we consider that disease as a parasitic disease. Very probably some of the diseases now known only as conta- gium or miasmatico-contagium will in future be transferred to the parasitic class, and this probability is expressed by what is known as the germ theory. To understand the controversies which have arisen on this point, cor- rect views of which are not only of theoretical interest, but of very great practical importance to the sanitarian, it is necessary to know something of the nomenclature of the subject,, which has become very confused and unsatisfactory, since the words bacteria, microzymes, germs, contagium, etc., are used by different authors, and by the same author, at different times, in different senses, and to this is due much of the disagreement which exists. That some diseases are due to the entrance of living organisms into the body is a very old theory, first set forth with some attempt at precision after the discoveries of Leeuwenhoeck were published. The history of the various speculations based on this theory, and on that of fermentations, is a curious and interesting one, but would be out of place here; and it need only be said that the views now held by the majority of physicians date only from the cholera epidemics of 1832 and 1849, and that they had no scientific precision prior to the well-known researches of Pasteur into the processes of fermentation and putrefaction and the minute organisms connected with them. In almost all fresh water, in dead and decomposing organic matter under ordinary conditions, and throughout the lower strata of the atmosphere, we find, upon examination with the highest powers of the microscope, my- riads of minute bodies which have the power of self-propagation when supplied with a suitable nutritive material, and some of which exhibit mo- tions in certain stages of development, in such a manner that we must class