BACTERIOLOGY OF WHOOPING-COUGH 15 



thoroughly the sputum is washed. In smears of the sputum they 

 sometimes appear as the only organism present. In a few cases 

 the leucocytes in the sputum were crowded with them, but generally 

 they were outside the cells. 



Morphology. The organism is a small, short, non-motile bacillus, 

 which does not take Gram's stain, does not have a capsule, and does 

 not form spores. It stains more deeply at the ends, especially with 

 methylene blue, and therefore may be mistaken for a small diplo- 

 coccus. It stains especially well with dilute carbolfuchsin. In 

 sputum the bacillus is nearly always single, but occasionally two or 

 three bacilli may be seen in a chain. Their morphological char- 

 acteristics in sputum are very uniform. In the culture, however, 

 it is quite different. In many of the strains there is a marked tendency 

 to chain and thread formation. Frequently the organisms occur as 

 coccus forms and in thick, curved, or S-shaped threads. Sometimes 

 threads may be seen reaching across the field of the microscope, and 

 much thicker than the single bacillus. As was stated, they are never 

 seen in smears direct from the throat, but may occur in the first 

 generation in the blood plates, or develop later. They are usually 

 more marked in a culture a few days old. When one meets these 

 for the first time he is convinced that he has a mixed culture or some 

 entirely different organism. These peculiar irregular forms agree 

 well with Pfeiffer's pseudo-influenza organisms, which he isolated 

 from cases of broncho-pneumonia. However, this fact should be 

 emphasized, that many of the strains do not show this tendency to 

 any extent under any circumstances, and, so far as this point is con- 

 cerned, agree with Pfeiffer's description of the real influenza bacillus. 

 As regards the size of the bacillus, the various strains all appear about 

 the same in sputum, and, compared with the few influenza bacilli 

 that I have been able to obtain, show practically no differences. 

 In cultures, however, bacilli of various strains from whooping-cough 

 vary in size so much among themselves that a comparison is difficult. 

 Certainly many of the whooping-cough strains are as small as organ- 

 isms from typical clinical cases of influenza. 



Cultural characteristics. The organisms from pertussis corre- 

 spond in their cultural characteristics in every way to Pfeiffer's bacillus. 

 It is a strict aerobe. On plates the colonies are small, moist and 



