424 INFLUENZA 



than 1:10. Davis, by inoculation of the fauces of a healthy man 

 with this organism, produced inflammatory change with febrile 

 reaction, but not the characteristic symptoms of whooping-cough. 

 There is presumptive evidence in favour of the bacillus being 

 etiologically related to the disease, though the matter cannot yet 

 be considered settled. M tiller's "trachoma bacillus" (p. 192) is 

 a member of the same group. All these organisms are very 

 restricted in their growth, and require the addition of blood or 

 haemoglobin to the ordinary culture media ; hence they are some- 

 times spoken of as hsemophilic bacteria. Some of the examples 

 are a little larger than the influenza-bacillus, and tend to form 

 short filaments, but others are quite indistinguishable. All of 

 them also seem to have very feeble pathogenic properties towards 

 the lower animals. At present it can scarcely be claimed as 

 possible to identify Pfeiffer's bacillus by its microscopic and 

 cultural characters. 



Experimental Inoculation. There is no satisfactory evidence 

 that any of the lower animals suffer from influenza in natural 

 conditions, and accordingly we cannot look for very definite 

 results from experimental inoculation. Pfeiffer, by injecting 

 living cultures of the organism into the lungs of monkeys, in 

 three cases produced a condition of fever of a remittent type. 

 There was, however, little evidence that the bacilli had under- 

 gone multiplication, the symptoms being apparently produced 

 by their toxins. In the case of rabbits, intravenous injection of 

 living cultures produces dyspnoea, muscular weakness, and 

 slight rise of temperature, but the bacilli rapidly disappear in 

 the body, and exactly similar symptoms are produced by 

 injection of cultures killed by the vapour of chloroform. 

 Pfeiffer, therefore, came to the conclusion that the influenza 

 bacilli contain toxic substances which can produce in animals 

 some of the substances of the disease, but that animals are not 

 liable to infection, the bacilli not having power of multiplying 

 to any extent in their tissues. 



Cantani succeeded in producing infection to some extent in 

 rabbits, by injecting the bacilli directly into the anterior 

 portion of the brain. In these experiments the organisms 

 spread to the ventricles, and then through the spinal cord by 

 means of the central canal, afterwards infecting the substance 

 of the cord. An acute encephalitis was thus produced, and 

 sometimes a purulent condition in the lateral ventricles. The 

 bacilli were, however, never found in the blood or in other organs. 

 Similar symptoms were also produced by injection of dead 

 cultures, though in this case the dose required to be five or six 



