THE FRIEDLANDER GROUP 671 



times clot in litmus mUk, they usually produce alkaU in neutral peptone water in 10 days, 

 they are M.R. positive and V.P. negative, some strains grow in citrate, most strains grow 

 in fresh ox bile, and many strains form HjS. (c) The third, according to Goshngs (1934), 

 comprises the Friedlander and Bart, arrogenes strains. These are the most active bio- 

 chemically, growing freely in fresli bile, producing gas from carbohydrate media, fermenting 

 lactose and amygdalin ^\■ithin 3 days and sucrose within 10 days, tm-ning neutral peptone 

 water either slightly acid or alkaUne, reducing htmus, utihzing sodium citrate and d-tartrate, 

 but not forming HjS. De Graaff (1936) and Wielenga (1937) would distinguish Fried- 

 lander's bacillus from Bad. aerogenes, though they are not in complete agreement on 

 the criteria that should be used for this purpose. 



Of reactions not studied by Goshngs or Wielenga, the indole test is generally nega- 

 tive ; nitrates are reduced to nitrites ; ammonia is formed from peptone ; methylene 

 blue is generally reduced in broth ; gelatin is not hquefied ; and there is usually an 

 abundant production of catalase. All these reactions, however, apply mainly to Fried- 

 lander and aerogenes strains ; the behaviour of rhinoscleroma and ozsena strains has been 

 less thoroughly studied. According to Hay (1932), one of the most characteristic featm'es 

 of the mucosus capsulatus group is their ability to ferment inositol, but this is likewise 

 shared by Bad. aerogenes. 



Antigenic Structure. — Till quite recently no satisfactory division of the Fried- 

 lander group had been made on the basis of antigenic structure. The main difficulty 

 was due to the fact that, though injection of the capsulated bacilli into rabbits 

 is able to give rise to an agglutinating serum, this serum has little action 

 except on non-capsulated organisms ; several attempts were therefore made to 

 rid the bacilli of their capsules. Porges' method (1905) was one of the most suc- 

 cessful. He suspended an agar cultiire in 10 ml. of saline, filtered through paper, 

 mixed it with a quarter of its volume of N/4 HCl solution, and heated for 15 minutes ; 

 it was cooled rapidly, and neutralized with N/4 NaOH solution. The resultant 

 suspension was homogeneous and non-viscous, and agglutinated with a specific 

 immune serum. Though this method undoubtedly removes the capsules, it often 

 renders the bacilli spontaneously agglutinable or agglutinable by normal serum. 

 Streit (1906) found that if the bacilli were grown on potato or potato agar, they 

 gradually lost their capsules, and became more agglutinable. Small and Julianelle 

 (1923) obtained the same result by growing them on agar for 24 hours, storing 

 the cultures in the ice-chest, and subculturing monthly ; after 1 to 2 years many 

 of the strains had lost their capsules. Agglutination tests made with non-capsulated 

 bacilli obtained in these ways gave, however, very inconstant results ; nor could a 

 method of analysis in which the natural capsular antigens were disregarded be 

 accepted as satisfactory. (Streit 1906, Beham 1912, Fitzgerald 1914, Coulter 1917, 

 Small and Julianelle 1923). 



Further work in America (Avery et al. 1925, Heidelberger et al. 1925, Julianelle 

 1926a, b, c) has largely cleared up the confusion. It would appear that the im- 

 munological reactions of the Friedlander group are similar to those of the pneu- 

 mococci, depending on the presence in the cell of two entirely different factors — 

 a polysaccharide in the capsule responsible for the type-specificity, and a nucleo- 

 protein in the soma responsible for the species-specificity. According to Julianelle 

 (1926a) there are three serological types, distinguishable by agglutination, absorp- 

 tion, precipitin, and protection tests, and a heterogeneous group (X) of strains 

 that have not yet been antigenically differentiated. If a serum is prepared 

 against Type A by injection of heat-killed encapsulated organisms, it will agglu- 

 tinate encapsulated baciUi of its own type, but not those of any other type ; 



