Preventive medicine was a blundering, incomplete science until bacteriology opened unheard-of possibilities for the prevention of disease. Before discussing some of the victories of preventive medicine it will be well to take a brief survey of the growth of the following subject:
SCIENCE OF BACTERIOLOGY
From the brilliant overthrow by Pasteur, in 1861, and by Koch and Cohn, in 1876, of the theory of spontaneous generation, we may date its modern growth. Wrapped up in this theory of spontaneous generation, upon which speculation raged centuries before the invention of the microscope, lies the history of bacteriology.
The ancient Greek and Roman philosophers wrestled with the question, and very interesting views of the relation of germ life to disease are preserved to us in their manuscripts. With the invention of the microscope we can mark the first positive step towards the goal of to-day. A Jesuit priest, Kircher, in 1671, was the first to investigate putrefying meat, milk, and cheese with the crude microscope of his day, and left us indefinite remarks concerning “very minute living worms” found therein. Four years after Kircher a Dutch linen merchant, Antonius von Leeuwenhoek, by improving the lenses of the microscope, saw in rain-water, putrefying fluids, intestinal contents, and saliva, minute, moving, living particles, which he called “animalculæ.” In medical circles of his day these observations aroused the keenest interest, and the theory that these “animalculæ” might be the cause of all disease was eagerly discussed. Pleincz, of Vienna, after much observation of various fluids, putrefying and otherwise, wrote in 1762 that it was his firm belief that the phenomena of diseases and the decomposition of animal fluids were wholly caused by these minute living things.
Notwithstanding such assertions, from his day on until Pasteur, Koch, and Cohn finally proved its misconceptions in 1876, the theory of spontaneous generation held the upper hand in all discussions upon the question.
The stimulus to research as to the causes of disease along the line of bacterial origin did not entirely cease to be felt, and the names of Pollender and Davaine are linked together in the first undoubted discovery of micro-organisms in disease, when the cause of anthrax, a disease of cattle, was solved in 1863. Following closely upon Davaine’s researches, the primary causes of wound infection were worked out, and to the efforts of the British surgeon Lister are due the great advances of modern surgery.
In rapid succession the presence of bacteria was clearly demonstrated in relapsing fever, leprosy, and typhoid fever; but far eclipsing all former discoveries, on account of the magnitude of the difficulties encountered and overcome, were the brilliant demonstrations of the cause of consumption and allied diseases, and that of Asiatic cholera, by Dr. Robert Koch in 1882 and in 1884 respectively.
From that time onward innumerable workers have satisfied the critical scientific world as to the causes of pneumonia, diphtheria, tetanus, influenza, and bubonic plague, besides many diseases of cattle, horses, sheep, and other animals and insects.
Having glanced hastily at the history of bacteriology, we may next consider some facts concerning the germs themselves. What are they? To the lay mind the words germ, microbe, bacterium, and bacillus often convey confused ideas of invisible, wriggling, worm-like creatures, enemies of mankind, ever on the watch to gain a stealthy entrance into our bodies, where they wreak harm and death. Scientifically considered, however, they are the smallest of living things yet known. They are not animals, but are members of the vegetable kingdom, and are possessed of definite yet varying shapes. They consist of a jelly-like substance called protoplasm, which is covered in and held in place by a well-formed membrane of a relatively hard and dense character, exactly similar in composition to the woody fibre of trees.