54 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



These features are sufficient to identify them for clinical 

 purposes. Cultures are difficult to obtain, since the organism 

 only grows in presence of haemoglobin — e.g., on agar tubes streaked 

 with sterile blood (see p. 85). Under these circumstances they 

 form very minute translucent colonies, much like those of the 

 pneumococci, and cultures have a great tendency to die out. 



The M. catanhaUs (Plate III., Fig. 5), the next most frequent 

 cause of clinical influenza, is a diplococcus which does not stain by 

 Gram, and which has a considerable amount of resemblance to 

 the other two non-Gram-staining diplococci, the gonococcus and the 

 meningococcus. It occurs in vast numbers in the sputum and 

 nasal mucus of influenza, in the nasal mucus of a "common cold," 

 and is a common cause of bronchitis of ordinary type. It is also 

 an occasional cause of sore throat, and is not infrequently met 

 with in the examination of supposed cases of diphtheria. The 

 resemblance to the two other organisms named arises from the 

 fact that it is frequently intracellular. There is not usually any 

 difficulty in distinguishing between the three, owing to the difference 

 in their habitat — the gonococcus affecting the mucous membrane 

 of the urethra or cervix, the meningococcus the meninges, and 

 the M. catavrhalis the nose, mouth, and respiratory passages. 

 There are minute morphological differences between the three, 

 and an expert can usually identify them in film preparations 

 from the body, but where there is any question of the nature of the 

 organism present cultures ought to be made. The M. catavrhalis 

 is the only one of the three which will grow on gelatin at the 

 room temperature. 



ANTHRAX 



Anthrax occurs in man in three forms. The most common is 

 cutaneous anthrax, or, as it is sometimes called, malignant pustule. 

 Pulmonary anthrax, or wool-sorter's disease, is much rarer, and 

 intestinal anthrax rarer still. The practitioner will find the greatest 

 assistance from a bacteriological examination in the cutaneous 

 form of the disease ; he may search for the specific bacillus in 

 the sputum in a supposed case of wool-sorter's disease, but he 

 must be careful in his interpretation of his result, as bacilli which 

 might be mistaken by an untrained observer, relying on the 

 morphological appearances alone, sometimes occur in the sputum. 

 The search for bacilli in the faeces in a supposed case of intestinal 

 anthrax must be relegated to an expert. 



