40 Veterinary Medicine. 



affection afterward recognized as hog cholera. Writers con- 

 jecture that it was imported into America from l^urope in im- 

 proved pigs, and from one European country to another in the 

 same way, but we have no absolute proof of times and shipments 

 and their immediate effects, so that these theories are but more or 

 less reasonable deductions from the familiar extensions of the 

 disease in more recent cases. Under the great comriiercial activity 

 of the latter half of the lyth century, the active movements of 

 animals by canal, steamboat and rail, and the massing together 

 in one market of many animals drawn from widely different 

 sources, hog cholera has made extraordinary extensions on both 

 sides of the Atlantic, until Friedberger and Frohner pronounce 

 the schweineseuche and schweinepest the most widely disseminated 

 and dangerous of swine epizootics, and .Dr. Salmon estimates the 

 losses in the United States at $10,000,000 to $25,000,000, per 

 annum. 



Bacteriology. Prior to 1885 bacteria had been found in the 

 different outbreaks of contagious fevers in swine, and the bacillus 

 of swine erysipelas had been demonstrated in 1882, but it was 

 only two years later (1884) that the motile bacillus choleras suis 

 was first described by Klein, and in 1885 that Salmon and Smith 

 described it as the essential cause of the disease, together with 

 its biological and cultural peculiarities. 



It is a short bacillus, 1.2 to 2/j. X 0.5 to o.S^t, but varying con- 

 siderably in size according to the stage of its growth and the 

 genera of animal or culture medium in which it is grown. It has 

 rounded ends and is usually in pairs connected by an invisible 

 band. It stains promptly in all the aqueous aniline colors, but 

 loses the stain in a solution of iodine (Gram's). Prolonged ex- 

 posure of artificial cultures produces an uniform stain, while a 

 transient exposure, and especially of bacilli obtained from the 

 tissues, stains them most deeply at the ends (polar) and periphery, 

 while the centre remains somewhat clear. This is less marked 

 than in the bacillus of swine plague, yet serves to show the rela- 

 tion between this microbe and the colon group. 



It is cerobic (facultative anaerobic), non-liquefying, and, in 

 fluids, very actively motile, the movements lasting for months in 

 preserved specimens (Smith). It grows luxuriantly in various 

 culture media, and especially in alkaline ones, at the room 



