STREPTOTHRIX HOMINIS 369 



bation at 37° C. These do not increase much in size, and after four weeks' 

 incubation are not mucli larger than a pin's head ; there is a tendency for the 

 colonies to cohere in flocculent masses. The growth is whitish in colour. Patho- 

 genicity for lower animals. — Two rabbits received intra-peritoneal injections of broth 

 cultures, but there were no obvious effects.* 



Other acid-fast members of the pathogenic streptothrix group 

 have been isolated by Birt and Leishman from a case of pleural 

 effusion ; by Eppiuger from an abscess of the brain ; by MacCallum 

 from peritoneal pus; by Nocard in "farcin du boeuf." These 

 organisms can, as a; rule, be differentiated from the tubercle bacillus 

 by morphological, cultural, and tinctorial properties. 



General Note on Differentiation of Acid-fast Organisms 



The acid-fast bacillus, pseudo-tubercle bacillus, and acid-fast 

 streptothrix may all be found to resemble the tubercle bacillus in 

 greater or less degree. It has been suggested that they are all of the 

 streptothrix genus. "Whilst they are all acid-fast they are not equally 

 resistant, and this fact assists in their differentiation. Broadly, none 

 of these forms can resist decolorisation with 25 per cent, sulphuric 

 acid for more than sixteen hours, whereas the tubercle bacillus can 

 withstand decolorisation for seventy-two hours (Coles). Hence, if 

 film preparations be made in the usual way, stained for seven minutes 

 with hot carbol fuchsin, and then decolorised with 25 per cent, sul- 

 phuric acid for sixteen hours, the only bacilli remaining red are 

 tubercle baciHi. If this method f aO, cultivation and inoculation tests 

 must be apphed. The former by culturing in broth at 30° C. (shows 

 growth in three days in non-tubercle bacilli), the latter by inoculation 

 of guinea-pigs. And here, as elsewhere, it is necessary to observe all 

 the characters before forming a diagnosis. 



* An excellent statement on the general characteristics and pathogenic action of 

 the genus Streptothrix will be found in the Trans, of the Path. Soc. of London, 

 1902, vol. 53, part i., pp. 56-127 (Foulerton and Price Jones). 



2 A 



