368 TUBERCULOSIS AS A TYPE OF' BACTERIAL DISEASE 



cultures up to three months old show no acid-fast portions when stained by the Ziehl- 

 Neelsen method. 



Cultural Characteristics. Grows freely in presence of oxygen, very scanty 

 growth under anaerobic conditions ; on all media, except potato, growth is distinctly 

 more active at 37 C. than at 22 C. ; old cultures, especially those in peptone beef 

 broth, have a faintly feculent odour. On gelatine at 22 C. Streak culture : obvious 

 growth is seen on third day, at first of an opaque white appearance, later may show 

 a very faint yellowish tinge. Growth sinks slowly into the medium, which gradually 

 liquefies. Stab culture : growth occurs along track of needle in the form of super- 

 imposed colonies, which have a somewhat flocculent appearance. On peptone-maltose 

 agar. After 24 hours' incubation at 37 C. there is some indication of growth; at 

 22 C. no obvious growth occurs within this period. After 72 hours' incubation at 

 37 C. there is a fair amount of growth, and rather less after incubation at 22 C. 

 The growth, at first of a faint drab or whitish tint, after longer incubation, becomes 

 usually of a faint yellowish colour. Cultures may yield a free formation of aerial 

 hyphae, giving a snowy appearance to the surface of the growth, or the surface may 

 assume a reticulated appearance, without any efflorescence. (For microscopic 

 appearances, see Plate 29.) On inspissated horse-serum. Growth is comparatively 

 scanty on this medium, appearing after 72 hours' incubation at 37 C. At the end of 

 twenty-eight days' incubation at 37 C. there is a dry, wrinkled, drab-coloured growth, 

 which has sunk slightly into the medium; no liquefaction. On potato. Growth 

 on this medium is equal at temperature 37 C. and 22 C. ; at the end of 48 hours' 

 growth appears as a brownish or faintly yellowish stain on the medium ; later, 

 growth usually assumes a cafe au lait colour; there is no pigmentation or 

 erosion of the medium. Surface efflorescence is seen only in cultures incubated at 

 37 C. , and not in cultures at 22 C. In peptone beef broth. After 48 hours' incu- 

 bation at 37 C. the appearance of some filmy growth is seen at the bottom of the 

 tube ; in older cultures growth appears as flocculent, more or less discoid colonies. 

 No pigmentation. (For microscopic appearances, see Plate 29.) In alkaline 

 litmus milk. Medium at end of 72 hours' incubation at 37 C. is of a faint pink 

 colour ; no coagulation. The pink colour changes to a dirty white, and the milk 

 clears gradually from the surface downwards, becoming at last of a brown colour. 

 Growth on peptone agar is about equal to that on peptone-maltose agar ; growth on 

 glycerine agar (1 per cent, glycerine) is less free than it is on either of the two pre- 

 ceding media. Diastatic action. No action of the sort is manifested within fourteen 

 days' incubation at 37 C. Resistance to heat. Sporulating cultures resist exposure 

 to moist heat at 70 C. for 20 minutes, but are destroyed by an exposure to the same 

 temperature for 30 minutes. Pathogenicity for lower animals. Not found patho- 

 genic for rabbits (intra-venous and intra-peritoneal inoculation), for guinea-pigs 

 (intra-peritoneal inoculation), or for tame mice (intra-peritoneal and subcutaneous 

 inoculation). 



2. Streptothrix hominis (Foulerton). 



Isolated from a case of pulmonary infection in a woman (especially from sub- 

 cutaneous abscesses). 



Staining Characteristics. Takes Gram's stain. A three-months' old culture from 

 glycerine-peptone agar showed no acid-fast portions when stained by the Ziehl- 

 Neelsen method. 



Cultural Characteristics. Growth was obtained in peptone-beef broth and on 

 solid media under ordinary aerobic conditions; no growth occurred on tubes of 

 peptone agar and glycerine-peptone agar incubated under anaerobic conditions. 

 Growth is more active at 37 C. than at 22 C. On peptone agar. Growth very 

 slow and scanty ; after several weeks' incubation small whitish, heaped-up, dry- 

 looking colonies, resembling somewhat the growth of 13. tuberculosis, are seen. On 

 glycerine agar and maltose-peptone agar. The amount of growth is very much the 

 same as in the last case, and of much the same appearance. On inspissated horse- 

 serum and inspissated ox-serum. Growth is very scanty ; the colonies sink slightly 

 into the medium. On potato. No growth was obtained. In peptone-beef broth. 

 Small globular colonies appear in the depth of the broth after about six days' incu- 



