THE INFECTIOUS DISEASES. 267 



injection. The statistics seem to indicate that among exposed persons 

 the mortality may be considerably reduced by this preventive inoculation. ' 

 An anti-plague serum, prepared by the immunization of horses, ha* 

 been used by Yersin with at least promising results. ' 



HJEMORRHAGIC SEPTICAEMIA. 



There are several bacilli which may be classed, as is done by Hueppe, Kruse, and others, 

 with the plague bacillus under the designation, the liamorrhagic septic&mia group. These 

 are mostly small, short, sporeless forms growing readily on the ordinary media as facul- 

 tative anaerobes, not fluidifying gelatin and decolorizing by Gram. Some of these are 

 motile, others not. Among these may be mentioned the bacillus of mouse typhus (B. 

 typhi murium), the bacillus of hog cholera (B. suipestifer), the bacillus of chicken 

 cholera (B. cholerae gallinarum), the bacillus of swine plague (B. suisepticus). Several 

 species related to these and to the plague bacillus are pathogenic in man ; thus the 

 B. hcemon-hagicus septicus of Babes, the B. Iwemorrhagicus of Kolb, the B. lusmorrliagicu* 

 velenoxus of Tizzoni and Giovanni. 



The recognition of these and related species may be of especial significance in con- 

 nection with the diagnosis of bubonic plague by cultures and animal inoculations. 3 



BACILLUS AEEOGENES CAPSULATUS (BACILLUS WELCHII, GAS 



BACILLUS). 



This bacillus was described in 1891-92 by Welch and Nuttall. Later 

 studies of Welch and Flexner and many others have confirmed the orig- 

 inal belief that the bacillus is a frequent excitant in man of a serious in- 

 fectious disease, characterized by a local or widespread serous and em- 

 physematous phlegmouous inflammation, frequently associated with 

 gangrene and general symptoms of a profound toxaemia. 



The Bacillus aerogenes is rather large, on certain media spore form- 

 ing, is often capsulated, and occasionally forms chains. It retains the 

 stain by Gram's method. It is anaerobic, growing readily in a variety 

 of artificial culture media. 



Babbits are not susceptible to even large intravenous injections of 

 pure cultures. But if they be killed soon after such inoculation, within 

 a few hours, at room temperatures, an abundant development of gas 

 occurs throughout the body. On the other hand, the subcutaneous in- 

 jection of a very small quantity of the fresh oedeniatous exudate is fol- 

 lowed by the typical local and general marks of infection. Guinea-pigs 

 are more susceptible than rabbits to inoculation, either with cultures or 

 fresh material, and develop characteristic lesions. 



While infection may occur without gas, in most cases before death 

 and especially after, there is an abundant formation of gas in the tis- 

 sues. This is largely hydrogen formed through the splitting by the 

 bacillus of either sugar or proteids. While the gas may be present in 



1 For summary of result of the Haffkine method see Forsyth, Lancet, December 

 12th, 1903; also Slaughter, Johns Hopkins Hospital Bull., vobxiv., 1903, p. 307. 



2 Critical summary and bibl., Netter, Arch, de Med. exp., t. xii., p. 86, 1900. 



3 For studies on various forms of haemorrhagic infection see Babes, Verh. d. deutschen 

 path. Gesellschaft, Bd. ii., p. 262, 1900; also Kitt, Kolle and Wassermann's "Handbuch 

 der Mikroorganismen," Bd. ii., p. 559. 



