34 MYCOLOGY 



diseases in plants will be considered at length in another section. 

 Most attention has been paid to diseases of animals and man due to 

 bacteria and the number of special works dealing with the subjects of 

 bacteriology, pathology, immunity and disease would form a library. 

 Nearly every phase of the relationship of bacteria to animals and man 

 has been cultivated, and microbiology has been placed on a firm founda- 

 tion, as a subject of human inquiry. The field is too vast for one man 

 to cultivate it, and hence, we find a narrow specialism perhaps more 

 than in any of the other departments of biologic investigation. 



An interesting phase of the relationship of parasite and host has 

 come recently into the scientific limelight. Dr. Erwin F. Smith in 

 the study of the organism which produces the crown gall of woody 

 plants, Pseudomonas tumefaciens (Fig. 143), finds that the growth and 

 formation of the tumors suggests the development of cancer in man. 

 He thinks the formation of tumors in plants away from the point of 

 infection suggests a similarity (Fig. 158). 



SYSTEMATIC ACCOUNT OF THE BACTERIA 



For the use of students who may not have access to larger works 

 on bacteria and who would like a short systematic account of the 

 bacteria the following synopsis is given. 



ORDER I. EUBACTERIALES.— The organisms of this order 

 are unicellular, or in plate-like, spheric, or filamentous coenobia, if 

 imbedded in a slimy matrix, then not of a definite form. 



Family i. Coccace^. — Single spheric cells. Division in one, 

 two or three directions. 



Streptococcus.- — Division always in one direction, coenobia, there- 

 fore, chain-like, cells without flagella. Pathogenic: 6'. erysipelatos, 

 specific germ of erysipelas to be distinguished with difficulty from S. 

 pyogenes. Not pathogenic: S. mesenterioides {Leuconostoc mesen- 

 terioides), occurring in mucilaginous masses in the molasses waste of 

 sugar factories, and its presence disastrous to the industry. 



Micrococcus. — Division in two directions, coenobia, sheet-like, 

 without flagella. Pathogenic: Micrococcus pyogenes aureus ( = 

 Staphylococcus pyogenes aureus), the cause of pus formation and 

 purulent discharge from wounds, M. gonorrhxce (= Gonococcus gonor- 

 rhcece) specific germ of gonorrhoea. Not pathogenic: M. aurantiacus, 

 luteus, cinnabareus producing pigments. 



