ON THE GERM THEORIES OF INFECTIOUS DISEASES. BY JOHN J. DRYSDALE, M.D., M.R.C.S. THE "pestilence that walketh in darkness" has from the earliest times affected so profoundly not only the happiness ERRATA IN DR. DRYSDALE'S PAPER "ON THE GERM THEORIES OF INFECTIOUS DISEASES." Page 5, line 7 of note, for " oxygen," read "water." governing bodies than for physicians. necessary that the efforts of the former should be guided by such knowledge of the nature and causes of these diseases as the science of the day can afford. Nor is such knowledge less to be desired for the people in general in order to counteract the baneful effects of ignorance and prejudice. It is a fact that, from the time of Thucydides down to the outbreak of the cholera in our own day, in all severe epidemics a false suspicion has prevailed that the wells or provisions were poisoned by supposed public enemies. To this groundless suspicion thousands of lives have been sacrificed, and it was the cause of the fearful persecution of the Jews in the fourteenth century. The simple knowledge of the fact of the universal prevalence of this suspicion, and, still more, the knowledge which medical science can now give with A ON THE GERM THEORIES OF INFECTIOUS DISEASES. BY JOHN J. DRYSDALE, M.D., M.R.C.S. THE "pestilence that walketh in darkness" has from the earliest times affected so profoundly not only the happiness of families, but the wealth of nations, and even the course of civilisation, that it may be deemed a fit subject to be brought before a non-medical Society. I hope that the bearing of such inflictions on human affairs may be also considered of a sufficiently general nature to allow its being taken as the topic of the Opening Address of the Session. When we consider the awful mortality of the great epidemics recorded in history-the Black Death of the fourteenth century having, for example, swept off one-quarter of the population of the old world in four years — and the almost total impotence of medicine for direct cure, we may indeed consider this a question more for statesmen and governing bodies than for physicians. Nevertheless, it is necessary that the efforts of the former should be guided by such knowledge of the nature and causes of these diseases as the science of the day can afford. Nor is such knowledge less to be desired for the people in general in order to counteract the baneful effects of ignorance and prejudice. It is a fact that, from the time of Thucydides down to the outbreak of the cholera in our own day, in all severe epidemics a false suspicion has prevailed that the wells or provisions were poisoned by supposed public enemies. To this groundless suspicion thousands of lives have been sacrificed, and it was the cause of the fearful persecution of the Jews in the fourteenth century. The simple knowledge of the fact of the universal prevalence of this suspicion, and, still more, the knowledge which medical science can now give with A certainty that no such poisons exist, ought to go far to prevent such aggravations of natural calamities for the future. And let not people fondly imagine that the days of national epidemics are over. On the contrary, there has been a constant succession of greater and lesser epidemics since the beginning of history, and the immunity of any generation from the greater plagues may be merely an interruption of the course liable to terminate any year by a fresh outbreak of some old or a quite new plague. For instance, the memory of the Sweating Sickness of 1485 was obliterated by the Plague of London, in 1499, but the former returned again unaltered in 1506; and again a third, fourth, and fifth time during the first half of the sixteenth century. Diphtheria has also reappeared again and again after being forgotten in intermediate generations, as also many varieties of spotted and typhous fevers and numerous other diseases. The subject is thus one of universal and abiding interest and concern to us all, so, without further preface, I will proceed to consider the light that may be thrown on these mysterious scourges of humanity by the so-called germ theories of which so much has been heard of late. § 1. Let us restrict our attention to those diseases the material exciting causes of which are termed, generically, miasms. Following a recent writer, * diseases arising from miasms may be divided into the miasmatic simple, the contagious, and those which partake of both characters, and hence called miasmatic-contagious. 1st. The contagious diseases arise from a contagious miasm or contagium, or specific excitant of disease, which is reproduced in the organism suffering from the specific disease. Under this head come smallpox, measles, scarlet fever, typhus, plague, glanders, &c. 2nd. Under the term miasmatic are comprehended malarious diseases, viz., the intermittent and * Liebermeister, in Ziemssen I., p. 25. remittent marsh fevers. Here the poison develops itself externally to the body, and is not reproduced therein so as to affect other men from thence, nor is it excreted thence to propagate itself in any other way. 3rd. The miasmatic-contagious comprehend cholera, typhoid, dysentery, and probably some others; here the disease is not readily, if at all, transmissible from person to person; nevertheless, these diseases never originate spontaneously or from purely malarious influences, but always after some person affected with them has been in the neighbourhood; so it is supposed the secretions from infected persons undergo development in favourable media out of the body. In other words, the reproduction of the miasm is partially performed out of the body. § 2. What is the intimate nature of this miasm or infectious matter? In the first place, as regards its physical state, it has been determined with respect to the vaccine and some other animal poisons, and is almost certain with the rest, that the specific power does not reside in anything which is gaseous, or liquid, or capable of solution, or diffusible from the medium in which it is contained. * Thus when we hear of sewage or paludal liquids or gases spoken of as the exciting causes of infectious diseases, it is to be understood that the true specific matter is a solid merely suspended in the liquid or gas. This at once cuts off a large number of both inorganic and organic substances from the category of possible causes of the specific disease. [See diagram]. Next * Dr. Lionel Beale first attributed the infective properties of vaccine and other contagious diseases exclusively to solid matter, and this was experimentally demonstrated afterwards, first by Chauveau and then by Dr. B. Sanderson, by the method of diffusion. Filtration was ineffectual for separating the extremely minute particles in which the contagion resides, from the matrix fluid. Chauveau found the same principle to apply to variola, pleuro-pneumonia, glanders, and sheep-pox. The experiments with the vaccine matter have been recently repeated with greater care and detail by Drs. Braidwood and Vacher, of Birkenhead, who have proved that the liquid diffused out from vaccine matter is totally devoid of infective power. |