600 VETEEINAEY HYGIENE 



they reduce the natural powers of resistance. In this way 

 they faciUtate a secondary infection by other organisms, 

 some of which are natural to the body and ordinarily harm- 

 less, but after the preliminary action of the pasturella 

 toxin become pathogenic. Thus in the horse may be pro- 

 duced catarrh, sore throat, influenza in its various forms, 

 and infectious pneumoiiia, the pasteurella paving the way 

 and other organisms, naturally saprophytic, completing the 

 process. 



A very good example is afforded by the disease distemper 

 which is produced by a pasteurella ; while the complications, 

 such as pneumonia, are brought about by an organism 

 normally present in the mouth and nasal cavities of the 

 animal, excited into pathogenic activity by exposure to 

 cold. 



It is convenient to consider catarrh, sore throat, in- 

 fluenza, strangles and contagious pneumonia together, as 

 modern bacteriology assigns to them a common cause, viz., 

 the microbe known as Pasteurella equi, supplemented in the 

 case of catarrh, strangles, and pneumonia by a streptococcus 

 which is probably identical in all these affections. 



Influenza, with its many varieties and complications, its 

 widespread or local ravages, its comparatively benign or 

 remarkably virulent forms, has been known for many years, 

 but the identity of the organism producing this protean 

 malady has only recently been made clear through the 

 work of Lignieres and others.* 



The degree of disease which this organism is capable of 

 developing may vary from a common catarrh, sore throat, 

 or simple fever, to ' pink eye,' pneumonia, or enteritis ; 

 even purpura is included in those diseases in which the 

 pasteurella paves the way for other organisms to build upon. 



* Full information on the subject, to which we acknowledge our 

 indebtedness, is given in an excellent address by Mr. H. Gray, 

 M.R.C.V.S., to the Eastern Counties Veterinary Association, Veter- 

 inary Record, March 19, 1904. See also a most valuable paper, ' Pneu- 

 monia in the Horse, its Etiology,' contributed by Mr. J. A. Dollar, 

 M.R.C.V.S., P.R.S.E., to the Proceedings of the National Veterinary 

 Association, 1902. 



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