ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 631 



Virulence and Immunising Powers of Micro-organisms.* — R. P. 

 ■Strong investigated the essential differences existing between two 

 strains of cholera spirilla of different degrees of virulence, particularly 

 in relation to the subject of their virulence and to the immunity to 

 which they give rise in inoculated animals. He found that the virulent 

 cholera spirillum possesses a greater number of bacteriolytic and agglut- 

 inable haptophore groups, or these groups are endowed with a greater 

 binding power for uniceptors and amboceptors than the avirulent ; the 

 number or the avidity of the bacteriolytic receptors possessed by a 

 bacterium is directly proportional to its virulence ; but the agglutinable 

 receptors do not follow this law, the agglutinable haptophore groups are 

 not necessarily present in the same proportion as the bactericidal ones. 

 The virulent organism is possessed with a greater number of toxic hapto- 

 phore groups than the nonvirulent. The binding power of the free 

 receptors of the organisms for bacteriolytic amboceptors in vitro is pro- 

 portional to the bactericidal immunity produced in animals by each, 

 which latter is in turn proportional to the virulence of the organisms 

 from which the receptors were extracted. The binding power in vitro 

 of the dead micro-organisms of different virulence for bacteriolytic 

 amboceptors is not in proportion to their toxicity. The bactericidal 

 immunity obtained by means of the inoculation with dead organisms of 

 different virulence or their extracts (obtained by autolytic digestion) is 

 proportional to the virulence of the living strains of the bacteria 

 employed. With the living organisms, while the bactericidal immunity 

 •obtained from the inoculation of animals with the virulent organism is 

 greater than that produced with the non-virulent, such immunity is not 

 in direct proportion to the virulence of the bacteria introduced. 



Bacillus Freudenreichii.f — F. Lohnis, in his account of the nitrogen 

 bacteria, gives the following description of Bacillus Freudenreichii 

 Migula. Slender round-ended rods lfj. broad, 2/*-4/t long, having a 

 tendency to form threads ; they stain well by the ordinary dyes, and by 

 Gram's method ; in young cultures the rods are actively motile, having 

 numerous long peritrichous flagella ; spore formation is especially well 

 seen on old potato cultures, the spores being small, elliptical (1/a-1*25/a) 

 and tending to lie nearer to one pole ; on ordinary gelatin plate growth 

 is relatively slow, the small surface colonies are white and blue by trans- 

 mitted light, round and rather ragged, of the colon type but much smaller ; 

 the centre portion is yellowish and finely granular, the margin sharply 

 defined : after ten days the colony has a diameter of about 320/t* ; the 

 round, sharply contoured, yellow, deep colonies remain small ; on urea- 

 gelatin plates similar colonies develop, but the growth is quicker, the 

 colonies having a diameter of 110^-130/t after four days. In gelatin 

 stab cultures the growth is irregular; at one time, even after 10 days, 

 only a fine grey thread is noticeable in the track of the stab, and growth 

 on the surface has ceased ; whereas on another occasion, with rather more 

 alkaline gelatin, a fine milky thread is seen after four days, and on the 

 surface a white transparent membrane with ragged margin, which after 



* Bureau Gov. Lab. Manila, 1904, No. 21. 



t Centralbl. Bakt., 2 ,e Abt., xiv. (1905) p. 719. 



