BIOLOGICAL PROPERTIES 515 



2. Cultural characteristics. 



Conditions of growth. The bacillus of soft sore does not grow on the 

 ordinary media. 



It would seem that Petersen was able occasionally to grow the bacillus on serum- 

 agar but his investigations have not been confirmed. Istamanoff and Akspiantz 

 as well as Lenglet employ macerations of human skin solidified with agar, but their 

 technique is obscure and their results unconvincing. The cultivation of the bacillus 

 has been made practicable by the investigations of Bezangon, Griffon and Le Sourd. 



The most suitable medium is the rabbit-blood-agar of Bezanyon and Griffon 

 (p. 53) and after that liquid rabbit-serum. All attempts to grow the organism 

 on the ordinary media failed even after acclimatizing the bacillus by sub- 

 cultivating it on a series of blood-agar tubes. 



The bacillus is aerobic and grows at 37 C. 



Blood-agar. After sowing surface cultures freely with pus from the sore 

 and incubating at 37 C. for 24 hours colonies appear which are " rounded, 

 raised, lustrous, and attain their maximum size in 48 hours ; they are then 

 greyish opaque and about 1-2 mm. in diameter. ' ' When the growth is removed 

 for microscopical examination it has a tendency to slip away from the needle 

 and is difficult to break up on a slide. 



Sometimes the colonies only appear after incubating for 48 hours and are 

 few in number. The growth is more abundant in sub-cultivations, in which 

 the colonies are very numerous and may attain the size of a pin's head, but 

 they never coalesce to form a continuous layer. 



Rabbit-serum. Growth is poorer in liquid serum than on the above medium. 

 The serum becomes slightly turbid and shows a few little flocculi floating in it. 



SECTION III. BIOLOGICAL PROPERTIES. 



Vitality and virulence. Pus from the sore will remain virulent for some 

 time if kept away from the air ; Ricord obtained positive results after inocu- 

 lating pus 17 days old. The virulence is preserved equally well in urine, 

 water, vaginal mucus, etc. Drying at ordinary temperatures seems to destroy 

 the virulence of the pus in 2436 hours ; heating for 18 hours at 37 C. or 

 for an hour at 42 C. also destroys the virulence (Aubert), but a temperature 

 of -16 C. has no effect on it (Jullien). The bacillus is quickly destroyed by 

 weak antiseptic solutions and by acids and alkalis. 



In cultures on blood-agar the bacillus retains both its vitality and its 

 virulence for a very long time : sub-cultures sown from cultures kept in the 

 incubator at 37 C. for more than 3 weeks give positive results, and after 

 eleven sub-cultures on blood-agar the bacillus will still give rise to a soft 

 chancre in man. But in cultures on liquid serum the vitality of the organism 

 is of short duration (Bezan9on, Griffon and Le Sourd). 



SECTION IV. DETECTION ISOLATION AND IDENTIFICATION OF 



THE BACILLUS. 



To determine the presence of the bacillus in the tissues microscopical 

 examination should be supplemented by cultivation experiments and by 

 inoculation. 



(a) Microscopical examination. Scrapings from the sore. Wipe away the 

 pus from the surface of the sore, lightly scrape the base of the ulcer with a 

 strong platinum needle and spread the material on slides, taking care not to 



