BACILLUS INFLUENZ.€ 455 
suitably diluted with salt solutiou, contains a virus which will pass an 
Lo Chanibcrland filter, and reproduce a syndrome in man which they 
regard as typical influenza. The virus is said to be ineffective when 
injected intravenously, although it was virulent when introduced 
subcutaneously. DuJarric and Riviere' have made similar observa- 
tions. Yamonouchi, Sakakami and Iwashima- have placed the filtrate 
of influenzal mucus suspended in salt solution which passed a Berkefeld 
filter in the naso-pharynx of several volunteer subjects, each of whom, 
excepting a few who had recovered from a previous attack, developed 
an infection which was diagnosed as clinical influenza, l^nfiltered 
mucus from the same cases, similarly treated caused a similar infection. 
On the other hand, rather extensive attempts to transmit the disease 
by direct inoculation and with the filtrates of influenzal secretions 
have been unsuccessful.'' The anaerobic, filter passing organism 
isolated by Olitsky and Gates, and named by them Bacterium pneumo- 
sintes^ has been the object of considerable study. It grows with diffi- 
culty in fresh ascitic fluid reinforced with fresh, sterile kidney tissue, 
under strictly anaerobic conditions, and it is culturally inert. It 
measures 0.15 to 0.3 microns in length and occurs as minute rods with 
rather pointed ends. It is non-motile, Gram-negative and subcultures 
on anaerobic blood-agar plates are small, round and clear. It grows 
at 37° C. D. and T. Thomson^ have prepared a vaccine containing 25 
millions of Bacterium pneumosintes per cc. detoxicated with j^q-^ 
NaOH, with which they claim to have had some success. Neverthe- 
less, Bacterium pneumosintes is not as yet generally accepted as the 
inciting factor of the disease. The etiology of influenza (La Grippe, or 
"flu") is still suh judice. 
Animal.— In^wema. is essentially a disease of man. Pfeiffer'^ has 
shown that mice, rats, guinea-pigs, swine, dogs and cats are refractory 
to infection with the living organism. The introduction of hemo- 
globin broth cultures of B. influenzae through the chest wall of monkeys 
frequently causes a transient febrile reaction, and a catarrhal bron- 
chitis, which, however, is not clinically comparable to influenza of 
man. The animals usually recover rapidly. Rabbits are susceptible 
to the endotoxin of the influenza bacillus.'^ The injection of large 
numbers of living or killed organisms causes dyspnea and a paralysis 
of the leg muscles. Frequently the animals die. Death probably 
results from endocellular poisons of the organisms.** Wollstein and 
Meltzer^ have produced experimental bronchopneumonia in dogs by 
1 Compt. rend. Acad. Sci., 1918, 167, 606. 
2 Lancet, 1919, 106, 971; Compt. rend. Acad. Sci., 1919, 168, 1346. 
3 Public Health Reports, 1919, 34, 33. 
* Jour. Exp. Med., 1921, 33, 125, 361, 373. 
^ Annals of the Pickett-Thomson Research Laboratory, 1925, 1, Part II, 229. 
« Ztschr. f. Hyg., 1893, 13, 357. 
" Pfeiffer: Loc. cit. Cantani: Ztschr. f. Hyg., 1896, 23, 265. 
* Ferry and Houghton: Jour. Immunol., 1919, 4, 233. Huntoon and Hannum: 
Ibid., p. 167. Parker: Jour. Am. Med. Assn., 1919, 72, 476. 
9 Jour. Exp. Med., 1912, 16, 126. 
