BACILLUS INFLUENZA ft 233 



tempts to cultivate it alone on plain agar or serum utterly failed. 

 He then tried smearing the agar with drops of blood, and his efforts 

 were completely rewarded. The necessary substance for their 

 development seems to be hemoglobin, and for this reason the or- 

 ganism is spoken of as " hemoglobinophilic." On blood agar 

 colonies appear at the end of eighteen hours as minute circular 

 almost transparent dots. Even on blood culture medium the 

 organisms very soon die. They will live indefinitely, however, if 

 transplanted every three or four days. Grown in symbiosis with 

 other organisms development is more rapid, and growth will occur 

 for several generations on ordinary agar without the addition of 

 hemoglobin. The organism is a strict ae'robe and multiplies 

 only at a temperature between 25 C. and 42 C. 



Resistance. The bacillus is extremely delicate and has only 

 very feeble powers of resistance. In dried sputum it dies within 

 twelve to forty-eight hours ; in water it does not live more than 

 two days ; it cannot withstand boiling for one minute or a tem- 

 perature of 60 C. for five minutes. 



Pathogenesis. B. influenzse is only slightly virulent for ex- 

 perimental animals ; the rabbit is moderately susceptible and the 

 guinea pig even less. There is no satisfactory evidence that they 

 ever contract the disease in a natural way. 



In man the organisms appear in enormous numbers in the 

 secretions of the nose, throat, and respiratory tract. Frequently 

 they invade the lung tissue, and lobular pneumonia, purulent 

 in character, results. The bronchioles become filled with leukocytes 

 and in tissue sections the bacilli may be seen packed in between 

 the epithelial and pus cells. The bacilli are rarely found in the 

 blood. They may, however, be present in the lesions accompanying 

 influenza. They have been found in inflammations of the middle 

 ear, in meningitis, conjunctivitis, cystitis, and peritonitis. 



Influenza may take a subacute form. Bacilli may remain latent 

 or only slightly virulent in the lung tissue for many months, and 

 then if by chance the body resistance is lowered they may become 

 active. 



Infection is undoubtedly transmitted directly from one indi- 



