IOWA ACADEMY OF SCIENCES. 69 



cilia which may be numerou.^ coniinp: from the periphery, as in Typhoid fever 

 Bacillus, or several from the end. or a single one at one end of the extremities. 

 Motion has recently been observed in a Micrococus. In some cases the cell-wall 

 is extensible, some species are provided with a gelatinous envelope, the thickness 

 and composition varies in different species. In some this sheath is a carbohydrate 

 nearly like cellulose or in some putrefactive species, it is an albuminoid known as 

 mycoprotein. In some cases these sheaths contain iron, other colors are sometimes 

 found in the sheath, blue, yellow, red, etc., but it may be questioned whether 

 these colors in all cases really belong to the sheath, although they do in some 

 cases. 



The contents consist of protoplasm which in some cases appears to be nearly 

 homogeneous, but in a number it contains alouminoid bodies. In Begqiatoa roseo 

 persicina it is colored according to Lansester''"'. In Clostridium butyricun small 

 refrigent granules occur that color blue on t;he application of iodine, in that respect 

 they are similar to |the granulose of starch. Deggiatoa alba and others contain 

 highly refrigent granules of sulphur which are readily made out. Nucleus occurs 

 as Buetschli' and others have shown. These authors believe that the nucleus is 

 large. Minot'" says, "This important discovery in conjunction with the extraor- 

 dinary power of proliferation in bacteria confirms our generalization that a small 

 proportion of protoplasm is essential to rapid growth." Koch, however, holds that 

 the nucleus is not distinctly separated from the remainder of the protoplasmic 

 mass. 



Bacteria are among the smallest of plants, they vary in size from 0.0001 milli- 

 meter ("lu) or less, to 0.004 (Bacillus crassus) in width, length varies greatly 

 Bacteria are ubiqutous occurring in soil, air, water, ice, snow, dust, animals' 

 plants. They are especially common in filthy and putrid substances; their use in 

 such places is so important that we shall discuss this at greater length in the 

 proper place. 



SYSTEMATIC POSITION. 



It will be seen from what has previously been said that'the earliest investiga- 

 tors variously arranged bacteria. It seemed certain to them, that they were ani- 

 mals, for had they not motion? The learned Ehrenberg in 1888 ascribed to some, 

 complicated digestive organs, owing to the way in which coloring matter was 

 taken up. He recognized the division Monadina and Vibrionia. 



We may now mention another systematist who still adhered to the animal 

 nature theory: Felix Dujardin in his "Historre naturelle des Zoophytes," 1841, 

 admirably figured the species in some cases, and it is worthy of note that this man 

 observed that these "Infusoria" brought about certain chemical changes. He 

 found that oxalate of ammonia which had been added to his culture material entirely 

 disappeared when the germs had been growing in it for a time. 



Perty, in 1852, indicated that some of these so-called animals were plants. 

 Two years later Cohn published an admirable paper on the microscopic algae and 

 plants in which he clearly indicated that the organisms in question were plants 

 and not animals. Nsegeli had previously recognized that some of the colorless 

 forms found on algae were fungi, they did not assimilate like algae. In 1857 he 

 brought all these forms together and called them Schizomycetes, a term generally 

 adopted by bacteriologists at the present time. 



?aQuart. Jour. Mic. Science, Vol. XIII, 1873, Vol. XVI. 



9 Ueber den Ban der Baeterien. 1890. 



10 Proc. American Association Adv. of Science, Indianopolis meeting, 1890, p. 284. 



