18 PRINCIPLES OF BACTERIOLOGY 



tarit steps which led up to the development of the science, and upon 

 which ate ^foundation pests,an which we shall see that the results obtained 

 \v<''-o gained only .through 1 long and laborious research, and after many 

 obstacles were met and overcome by indomitable perseverance and 

 accurate observation and experiment. 



The first probably authentic observations of living microscopic 

 organisms of which there is any record are those of Kircher, in 1659. 

 This original investigator demonstrated the presence in putrid meat, 

 milk, vinegar, cheese, etc., of "minute living worms," but did not 

 describe their form or character. 



Not long after this, in 1675, Leeuwenhoeck observed in rain-water, 

 putrid infusions, and in his own and other saliva and diarrhoeal evacua- 

 tions living, motile " animalculse" of most minute dimensions, which 

 he described and illustrated by drawings. Leeuwenhoeck practised the 

 art of lens-grinding, in which he eventually became so proficient that 

 he perfected a lens superior to any magnifying glass obtainable at that 

 day, and with which he was enabled to see objects very much smaller 

 than had ever been seen before. "With. the greatest astonishment," he 

 writes, "I observed distributed everywhere through the material which 

 I was examining animalcules of the most microscopic size, which 

 moved themselves about very energetically." The work of this observer 

 is conspicuous for its purely objective character and absence of specu- 

 lation; and his descriptions and illustrations are done with remarkable 

 clearness and accuracy, considering the imperfect optical instruments 

 at his command. It was not until many years later, however, that any 

 attempt was made to define the characters of these minute organisms 

 and to classify them systematically. 



From the earliest investigations into the life history and properties 

 of bacteria micro-organisms have been thought to play an important 

 part in the causation of infectious diseases. Shortly after the first 

 investigations into this subject the opinion was advanced that puerperal 

 fever, measles, smallpox, typhus, pleurisy, epilepsy, gout, and many other 

 diseases were due to contagion. In fact, so widespread became the 

 belief in a causal relation of these minute organisms to disease that it 

 soon amounted to a veritable craze, and all forms and kinds of diseases 

 were said to be produced in this way, upon no other foundation than 

 that these organisms had been found in the mouth and intestinal con- 

 tents of men and animals, and in water. 



Among those who were especially conspicuous at this time for their 

 advanced views on the germ-theory of infectious diseases was Marcus 

 Antonius Plenciz, a physician of Vienna. This acute observer, who 

 published his views in 1762, maintained that not only were all infectious 

 diseases caused by micro-organisms, but that the infective material 

 could be nothing else than a living organism. On these grounds he 

 endeavored to explain the variations in the period of incubation of the 

 different infectious diseases. He also insisted that there were special 

 germs for each infectious disease by which the specific disease was 

 produced. Plenciz believed, moreover, that these organisms were 



