But the conceded duality of these two diseases as they occur in typical examples in swine, does not account for all the infectious fevers of swine, in which these microbes or others closely allied to them may figure. Salmon, Smith and their coadjutors describe double infections in the same system, in which both the bacillus choleræ suis and the bacillus pestis suis figure, and in which there result a combination of symptoms and lesions, that together represent both of these germs. It may be that one or other of these germs in a given outbreak, shows a predominance in potency so that the symptoms are more characteristic of it than of its companion; it may be that the more potent germ kills the victim, quickly by an acute septicæmia and gross lesions that would apply almost as well to one germ as to the other; or it may be that both act moderately and the attack is protracted with resulting lesions in both lungs and bowels that respectively suggest the plague and the cholera. Then as regards varieties in the individual germ. Th. Smith recognizes this as a frequent condition and describes no less than seven different types of bacillus choleræ suis which he had studied and which varied in morphology, cultural qualities and virulence. Lignieres found that the virulence especially of bacillus suis pestis is very easily affected by successive passages through the bodies of small experimental animals. We ought not to be surprised then if we find in different epizoötics, in different countries and even in the same, bacilli which for the time at least show characteristics different from those to which we have been accustomed. These give us varying phases of septicæmia which however come together in one great class. Two of these types which have been placed on record may be here named. For others see septicæmia hæmorrhagica of cattle and sheep. =McFadyean’s Swine Fever Bacillus.= The characters of this microbe found constantly by McFadyean in swine fever, approximates closely to the hog cholera germ in morphology and motility and in its deadly action when eaten, while it approaches toward the swine plague germ in its cultural habits on potato, gelatine and agar, and in alkaline culture liquids, and finally it differs from both in the absence of pathogenesis to Guinea pigs and in its very moderate action on rabbits. The symptoms and lesions of the _swine fever_ of Great Britain are those of the _hog cholera_ of America rather than of swine plague.