484 INFLUENZA 



able numbers in a large proportion of cases of this disease 

 (p. 485). Miiller's " trachoma bacillus " (p. 226) is a member of 

 the same group, as is also Cohen's bacillus of meningitis. 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 sometimes spoken of as hcemophilic 

 bacteria. Some of the examples are a little larger than the 

 influenza bacillus, and tend to form short filaments, but others 

 are quite indistinguishable. Most 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 in- 

 jection 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 symptoms of the disease, but that animals are not liable to 

 infection, the bacilli not having power of multiplying to any 

 extent in their tissues. Wollstein has found that a fatal cerebro- 

 spinal meningitis can be produced in monkeys by the sub-dural 

 injection of virulent cultures ; and that, in certain circumstances, 

 this affection may be cured by means of an anti-influenza serum 

 obtained from the goat. 



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 in- 

 fecting the substance of the cord. An acute encephalitis was thus pro- 

 duced, 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 times larger. 

 Cantani therefore concludes that the brain substance is the most suitable 

 nidus for their growth, but agrees with Pfeiffer in believing that the 



