BACILLUS OF DUG KEY 463 
Davis,^ which consists essentially in sterili'-^ing the skin over an 
unbroken bubo and aspirating the contents with a hypodermic needle 
which has been maintained at body temperature.^ The material is 
introduced directly upon the surface of blood agar.^ If the ulcers or 
buboes have opened, they may be cleaned with sterile gauze, dried, 
then ])ainted with tincture of iodine and covered with sterile gauze. 
Inoculations upon blood agar are made from the pus which collects 
imder the gauze within twent>'-four hours. Nicolau and Banciu'* 
state that peptone added to human blood is a better medium. 
The colonies are usually visible after twenty-four hours' incubation 
at 37° C. They appear as raised, shining, grayish droplets with a 
pearly luster. They die out rapidly at room temperature, but may be 
kept alive at body temperature for some days. The colonies are 
remo^'ed from the medium with some difficulty, for they tend to slip 
away from the platinum needle. Subcultures tend to increase some- 
what in luxuriance of growth, and by frequent transfer the organism 
may be kept alive for weeks provided the growths are maintained at 
37° C. Teague and Deibert^ have found that rabbit's blood alone is an 
excellent culture medium. Blood is withdrawn with aseptic precau- 
tions, and allowed to clot in small test tubes (4 x | inch, 1 cc. of blood 
to a tube). These are heated to 37° C if inoculated at once, or left in 
the ice-box to clot. The material from the ulcer is inoculated into the 
serum, and examined after a twenty-four-hour incubation for Gram- 
negative streptobacilli. Other organisms, especially cocci, may also 
be present. The appearance of the bacillary chains is distinctive and 
diagnostic. 
The bacillus of Ducrey is an aerobic organism which is not resistant 
to drying. The pus becomes non-infective after one or two days' 
desiccation. Weak antiseptics quickly destroy it. 
The products of growth are unknown. 
Pathogenesis. — It is non-pathogenic for ordinary laboratory animals. 
Fontana/ however, has reported successful inoculations of the cornea of 
rabbits with the organism. Tomasczewski^ claims to have reproduced 
a chancroid in a monkey (Macacus) by the injection of a blood-agar 
culture obtained from a bubo. This same culture also produced a chan- 
croid when inoculated into a man. Several successful inoculations in a 
man are recorded which appear to establish satisfactorily the etiological 
relationshi]) of the bacillus of Ducrey to the lesion. 
Bacteriological Diagnosis. — ]. Microscopic— \i material be remoNed 
carefully from the base of an ulcer and spread gently u])on a glass 
' Jour. Med. Res., 1903, 9, 401. 
2 Both the syringe and the blood agar should be warmed to body temperature before 
use, because the organism rapidly loses its viability at room temperature. 
' Blood agar for this purpose is prepared by adding defibrinated human or rabbit 
blood to agar; the medium is heated to 56° to 60° C. for thirty minutes to destroy 
natural bactericidal substances, and incubated for twenty-four hours to insure sterility. 
^ Compt. rend. Soc. de Biol., 1926, 95, 146. ^ jour. Urol., 1920, 4, 54.3. 
6 Centralbl. f. Bakteriol., orig., 1910-1911, 57, 433. 
" Deutsch. med. Wchnschr., 1903, 29, 466. 
