SAPROPHYTIC AND PATHOGENIC MICROORGANISMS 17 



SforotrichufUy various actinomycetes such as those causing lumpy jaw of 

 cattle, and certain other organisms. Henrici (396) divided fungus in- 

 fections of animals into two groups: first, superficial mycoses, compris- 

 ing moniliases and dermatomycoses, that are caused by a variety of 

 fungi widely distributed in nature j and, second, deep-seated infections, 

 namely, aspergillosis, sporotrichosis, and blastomycosis, with a marked 

 tendency to restricted distribution. The latter were said to be caused 

 primarily by saprophytic forms, including varieties capable of chance 

 survival and of multiplication when accidentally introduced into ani- 

 mal tissues. 



Walker (952) suggested that the partly acid-fast coccoid, diph- 

 theroid, and actinomycoid organisms that have been cultivated repeat- 

 edly from leprosy are merely different stages in the life cycle of the 

 same form. The causative agent of leprosy, like certain pathogenic 

 actinomycetes, is believed to be a facultatively parasitic soil organism, 

 probably of wide but irregular distribution. Leprosy was thus looked 

 upon primarily as a soil infection, brought about presumably through 

 wounds J a secondary means of infection by contagion was not excluded. 

 A comparison of cultures obtained from rat leprosy, human leprosy, 

 and bacteria of soil origin led to the conclusion that the strains from all 

 three sources were identical ; human and rat leprosy were said to have 

 the same etiology and endemiology, finding a normal habitat in the soil. 



An interesting relationship has been shown to exist between Texas 

 fever and the capacity of cattle tick {Boofhilus bovis)^ the parasite car- 

 rier, to persist in the soil (836). The causative agent is an organism 

 with protozoan characteristics. It persists in southern pastures where 

 the carriers survive from one season to the next and keep the cattle con- 

 tinuously infected. The disease is of little importance in northern re- 

 gions, the ticks being destroyed during the winter. When northern cat- 

 tle are moved to southern pastures, they become subject to the disease. 



Pathogenic microorganisms capable of surviving in the soil have pre- 

 sented important economic problems to farmers raising hogs, cattle, 

 poultry, and other domestic animals, but disease incidence through this 

 source has been greatly diminished by the proper practice of sanitation. 

 The rotation of crops has been utilized for the purpose of overcoming 

 these conditions, several years usually being required to render infected 



