BACTERIOLOGY OF WHOOPING-COUGH n 



Upon blood-agar plates the varieties of bacteria appear so char- 

 acteristic that after some experience one can differentiate them with 

 a considerable degree of certainty. The pneumococcus, as a rule, 

 has a typical greenish halo about the colony, and the streptococcus 

 has usually a wide clear zone of hemolysis. Sometimes diphtheria 

 colonies appear practically identical with the streptococcus, though 

 as a rule the colony is whiter and more elevated and the zone of 

 hemolysis not so wide. Not infrequently the zone is absent. The 

 influenza-like organisms form small transparent delicate blue colonies 

 without any zone of hemolysis. Under the microscope, they 'are 

 nearly homogeneous, with a regular margin. The colonies of M. 

 catarrhalis may at first be confused with the influenza-like colonies. 

 There is no zone of hemolysis, the colony is larger, more elevated, 

 and usually darker in color. The margin is irregular and the center 

 is coarsely granular. Some non-hemolytic Grampositive diplococci, 

 occasionally met with in the first 24 hours, may be mistaken for 

 influenza-like colonies, but in smears they are readily distinguishable. 



In Table i is given a summary of the cases of whooping-cough 

 examined, with data indicating the more important organisms found. 

 Under the various headings the approximate number of organisms 

 is represented by + signs. 



Of the 61 cases examined there were 33 males and 28 females; four of them were 

 under one year of age and three were adults. The examinations were made during 

 the fall, winter, and spring of 1904-5. At no time during this period was there an 

 epidemic of influenza. In eight of the cases, bacilli belonging to the diphtheria group 

 were found in the sputum. Most of these organisms had granules, and they usually 

 produced hemolysis on the blood plates. In none of these eight cases were they 

 numerous, and none gave a history of a recent attack of diphtheria, nor did any of 

 them develop it later. Several of these organisms were given to Dr. Hamilton for further 

 investigation. In one case, No. 33, the child had a well-developed, typical case of 

 whooping-cough with no clinical evidence of diphtheria. A swab was obtained from 

 the throat, which upon examination showed numerous influenza-like organisms, but 

 no diphtheria bacilli, in smear or upon the blood-agar plates. Five days later the 

 patient appeared with a well-developed membrane showing on examination many 

 typical diphtheria bacilli, together with some influenza-like organisms. 



Under the streptococcus group are included the Gram-positive 

 cocci, whose small, delicate blue colonies have a wide, clear zone 

 of hemolysis about them. In like manner, under the pneumococcus 

 group are included the small colonies appearing in the blood plates, 

 and surrounded by a green zone. While such a differentiation of 



