INFLUENZA 6 1 



mencing dose is 5 millions. Vaccines obtained from cultures 

 on boiled blood agar seem but very slightly irritating, and 

 doses of 200 millions or more may be used. 



The M. catarrhalls (Plate III., Fig. 5), the next most fre- 

 quent 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 examina- 

 tion 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 mem- 

 brane of the urethra or cervix, the meningococcus the 

 mening'es, and the M. catarrhalis the nose, mouth, and respira- 

 tory passages. There are minute morphological differences 

 between the three, and an expert can often identify them in 

 film preparations from the body, but where there is any ques- 

 tion of the nature of the organism present cultures ought to 

 be made. The M. catarrhalis is the only one of the three 

 which will grow on gelatin at the room temperature. The 

 growth is more abundant at the body temperature, and con- 

 sists of spreading white or grey colonies. 



Vaccine treatment is fairly satisfactory, the disease often 

 clearing up quickly after two or three doses, and the patient 

 seems to show a certain amount of immunity for some months 

 after. The dose should be 100 to 500 millions. 



B. septus is another frequent cause of catarrh of a form 

 which may fairly be grouped under the clinical term influenza. 

 It is a short, Gram-positive bacillus which is frequently mis- 

 taken for the pneumococcus, but it has no capsule. In young 

 cultures it is a short oval rod; in older ones there is an 

 unstained band (from which it derives its name) across the 

 centre of the rod. On the whole, vaccine treatment does not 

 seem very satisfactory. The doses should be 100 to 250 mil- 

 lions. Sometimes the vaccine is extremely irritating, so that 



it is perhaps wiser to begin with not more than 50 millions. 



