simple beginnings along this line, their knowledge of bacteria as they are known today was very limited indeed. Even in 1838, when Ehrenberg published his description of the types of organisms found in infusions, microscopes had not yet been developed to a place where even large bacteria could be studied with any satisfaction.
By 1872, Ferdinand Cohn (Untersuchungen über Bacterien. I. Beitr. z. Biol, d. Pflanzen., 1, Heft 2, 1872, 187-222), the botanist, began to understand that a great variety of types of bacteria were in existence, and he was able to arrange an outline classification on which later classifications of bacteria have been built. However, his first outline classification of bacteria was scarcely published before he felt that he should have expressed the relationships of the bacteria to the simplest types of algae in a more intimate way. He therefore, in 1875 (Untersuchungen über Bacterien., II. ibid., 1, Heft 3, 1875, 141-207), drew up a second classification in which he integrated the known groups of bacteria with known groups of blue-green algae in a class, the Schizophyta. This arrangement assumed that the bacteria had a much more intimate relationship to the blue-green algae than the true fungi have to the green, red and brown algae.
It should be noted that early classifications of bacteria were based primarily upon structural characters, particularly the shape of the cells. This was a natural development, as morphological characters had been found to be useful in drawing up natural classifications of higher plants and animals. It is also quite natural that workers who drew up these classifications should have regarded the spherical organisms that they found as being primitive in nature. Little was known at that time of the distribution of bacteria in nature. It was not until later that it came to be realized that the bacteria that are spherical in shape are normally found on the skin or in secretions of skin glands (milk and other dairy products, etc.) of vertebrates. Few cocci exist as free-living forms in water or soil. Likewise, when physiological studies were made, it was found that the cocci require comparatively complex foods for their existence. Few modern classifications retain the arrangement in which cocci are placed first as suggested by Cohn in 1872.
Others have developed the early classifications[1] drawn up by Cohn, with many individuals contributing to the development of a better and better understanding of the evolutionary development of the bacteria. In the 1890's, two groups of individuals undertook the publication of manuals describing the known species of bacteria. These two groups exercised a great influence on the development of systematic bacteriology.
Migula (Arb. Bact. Inst., Karlsruhe, 1, 1894, 235-238; in Engler and Prantl, Natürlichen Pflanzenfamilien, Schizophyta, 1 Teil, 1a, 1895, 1-44) and his students began their work at Karlsruhe, Germany, in the early part of the 1890's, publishing various papers and books, the last of which was Migula's
- ↑ For a more detailed discussion of outline classifications developed by bacteriologists, see Manual, 3rd ed., 1930, 1-23; and Manual, 6th ed., 1948, 5-38.
