IOWA ACADEMY OF SCIENCES. 75 



ments with the blood of diseased animals. It was also shown as early as 1865 

 that sputum taken from tubercular patients would produce tuberculosis. As yet, 

 however, the eridence was not conclusive. In 1S77 Koch publi.'^hed the results of 

 his work on this disease, in which he showed conclusively that this special bacillus, 

 which he had isolated from diseased animals and cultivated outside of the animal 

 body, produced typical anthrax; that in the animal only the vegetative condition 

 occurred, but when the animal dies these rods break up into spores; that infection 

 in cattle and sheep commonly results from the taking up of spores while grazing 

 in an infected pasture. The organism thus lives a dual life, one in the animal and 

 one in the field. 



In ordinary cultures, spores are readily formed and these retain their vitality 

 for a long time. The writer has found that these when kept in silk threads retain 

 their vitality for at least six years. We mention this disease in particular because 

 it shows what rules must be followed in bacteriological research. The classic 

 canons of Koch must ever be obsei'ved, and these are, first, constant presence of 

 the germ with the disease; second, isolation and cultivation of the germ; third, 

 successful innoculation experiments with the germ isolated, and followed by the 

 same disease; fourth, this germ must be the same as in the original diseased animals. 

 Dr. Russell^" well says that these canons are just as applicable to phytopathology 

 as in animal diseases. For my own part, I am sorry to say that so many bacterial 

 diseases of plants have been described in which these canons have not been 

 observed. But to follow through in detail the various stages of the history of this 

 part of bacteriology, however interesting it is, would make this paper entirely too 

 long. We shall therefore touch only upon the more important points. 



Let us briefly consider the pyogenic organisms and their relation to septic 

 infection. The lengthy disputes between different investigators on the subject of 

 septic infection and the causal relation to the same and definite micro-organisms had 

 a most excellent champion in Weigert,^' who, in an able paper, set aside the gen- 

 erally accepted theories, that septic infection resulted from poisonous products of 

 ordinary saprophytic germs, or that certain changes occurred in the body before 

 the germs could develop. It was the old story of Justus von Liebig.'s who strongly 

 argued that germs and fungi follow a diseased condition. Weigert especially empha- 

 sized the importance of recognizing bacteria in different diseases. He should receive 

 much credit for having done a great deal towards perfecting methods of staining 

 bacteria. 



The pyogenic microbes have been a rich field for investigators. For is not this 

 subject of great importance to the physician? Almost daily he meets with the 

 germs in question. They are concerned in such diseases as septicismia, pytemia 

 and erysipelas. Then, too, these cocci are found in diphtheria. The forms of 

 septicaemia occurring in lower animals are numerous, as Koch^^ first showed. A 

 form of MicrococcKS commonly placed in the genus Streptococcus h widely distrib- 

 uted in nature, and also produce septicaemia in lower animals. Dr. V. A. Moore has 



3fiBacteria in their relation to vegetable tissues. Dissertation presented to the 

 Board of University studies for the degree of Doctor of Philosophy, Johns Hopkins 

 University. Freidenwald Company, Baltimore, 18!t2: pp. 41. 



'^Ueber pockenaehnliche Gebilde in parenchymatosen Organen und deren Bezle- 

 hung zu Bacterieneolnlen. Breslau, 1875. See Loeffer Die Geschichtliche Entw, etc, p. 

 203. 



38Chemistry. in its application to Agriculture and Physiology, edited by Lyon 

 .Playfair, Philadelphia. T. B. Peterson, Part Second, pp. 87, 119. 



s»Wundinfectionskrankheiten, Leipzig, 1878. Mith. d. kais- Ges. Amts Vol. T. 



