BACILLUS PERTUSSIS 457 
purulent masses by ])reference, and streaked out radially from the 
drop of blood. After twenty-four to forty-eight hours' incubation 
the plate is examined with a lens for Aery minute, clear, homogeneous 
colonies which should be removed to blood-agar slants. When growth 
occurs transfer some of it to plain agar. No further dcAelopment 
takes place unless some blood has been removed with the organisms. 
The failure of the bacteria to develop on media free from hemoglobin 
is distinctive. 
3. Serolngical.— The serum diagnosis of influenza has been unsuc- 
cessful, although Fleming' has demonstrated agglutinins in the blood 
of influenza patients which agglutinate the influenza bacillus in low 
dilutions, and Rapoport'-^ obtained complement-fixation with the serum 
of convalescents in about one-half the cases tried. These observations 
do not imply, howe\'er, a primary etiological action by the Pfeiffer 
bacillus. 
Dissemination and Prophylaxis. — Influenza bacilli are distributed 
chiefly by droplet infection. Carriers are said to be common. Prophy- 
laxis is the same as for any respiratory disease. 
BACILLUS PERTUSSIS. 
The etiology of pertussis (whooping cough) has been a subject of 
controversy for several years. The problem is complicated by the 
rather general occurrence of influenza-like bacilli in the sputum and 
bronchial exudate from cases of whooping cough. A clean-cut dift'eren- 
tiation between these influenzoid bacilli and B. pertussis described 
by Bordet and Gengou^ has been difficult and has doubtless led to 
confusion in the past. It is now rather generally conceded that the 
Bordet-Gengou bacillus stands in about the same position with refer- 
ence to whooping cough that the Pfeifter bacillus exhibits in reference to 
the causation of influenza. 
Morphology. — B. pertussis is somewhat larger than B. influenza:', 
measuring 0.3 micron in diameter and varying in length from 0.5 to 
1.5 microns, the average length being about 1 micron. It occurs singly 
and in groups, less commonly in pairs. The organism has rounded 
ends; frequently it is almost ovoid in shape. The organism is non- 
motile and possesses no flagella. Neither capsules nor spores have 
been demonstrated. It stains poorly with ordinary anilin dyes and 
is Gram-negative. Carbol methylene blue, carbol toluidine blue and 
dilute carbol-fuchsin stain it readily. Methylene blue is also a satis- 
factory stain. The organisms stain irregularly, particularly when 
grown in artificial media. In young cultures and in sputum they 
appear frequently with the ends stained more dee])ly than the center, 
resembling in this respect the influenza bacillus. 
1 Lancet, 1919, i, 138. 
2 Jour. Am. Med. Assn., 1907, 48, 1563. 
3 Bull. Acad, de med. Belgique, July, 19 6; Am. Inst. Pasteur, 1 00, 20, 731. 
