842 THE FILTRABLE VIRUSES 



6. Wash for 1 or 2 minutes in 50 per cent, alcohol, pass rapidly through absolute 

 alcohol, and xylol. Mount in balsam. 



Celli, and de Blasi, and others regard the Negri bodies as parasites which at 

 a, certain stage in their life history are so small as to be capable of passing 

 through niters, and consider that it is these minute forms which originate 

 the infection. Remlinger holds that the Negri bodies are merely changes in 

 the nerve cells following the infection of the latter by the ultra-microscopic 

 parasite of the disease. 



SECTION X. FILTRABLE VIRUSES IN THE PASTEURELLOSES. 



1. Distemper. Carre by filtering the nasal discharge of dogs infected 

 with distemper obtained a liquid which though apparently sterile produced 

 all the symptoms of distemper when inoculated into young dogs. [M'Gowan 

 has isolated a gram-negative bacillus from the respiratory passages of animals 

 suffering from " distemper " and brings forward evidence to show that this 

 organism is the cause of the disease (p. 459)]. 



2. Infectious anaemia of horses. Carre and Vallee, by filtering through a 

 special bougie rather more porous than Berkefeld V a mixture of one part of 

 serum from a horse suffering from this disease and four parts of normal 

 saline solution, obtained a virulent nitrate. When this filtrate is inoculated 

 into the jugular vein of an horse in doses of 500 c.c. it produces, after an 

 incubation period of 6 days, an anaemia which runs a characteristic course 

 and which can be transmitted from one animal to another. The virus will 

 also pass through a Berkefeld V or Chamberland F or B but the incubation 

 period under these circumstances is of longer duration. 



3. Bird diphtheria. ^tiologically bird diphtheria is a totally different 

 disease from human diphtheria. Guerin thought it was due to a cocco- 

 bacillus belonging to the Pasteurella group which he found in the heart 

 blood of infected birds : this organism on inoculation however gave rise to 

 a fatal septicaemia quite different from the naturally acquired disease. 



By grinding up in normal saline solution the nictitating membrane of a 

 fowl which had been infected with a thread dipped in an emulsion of a false 

 membrane, Bordet obtained an emulsion which produced in fowls the typical 

 false membranes of bird diphtheria. When this emulsion was sown on 

 blood agar, the only visible growth consisted of a few colonies of adventitious 

 organisms : but by scraping the agar where there was no visible growth with 

 a platinum wire, and transferring the scrapings to a little drop of water and 

 rubbing the mucous membrane of the mouth with the emulsion, false mem- 

 branes were produced in a normal fowl. Serial cultures can also be obtained 

 and occasionally extremely small colonies are visible. Under the micro- 

 scope an emulsion of the cultures shows very large numbers of small granular 

 dots generally collected together in masses. This organism and that of 

 pleuro-pneumonia seem to be the smallest yet cultivated. 



According to Carnwath, this filtrable virus appears to be identical with 

 that of molluscum contagiosum of birds (vide ante). In an epizootic of 

 diphtheria among birds investigated by him the virus produced indifferently 

 molluscum contagiosum, or diphtheria according as to whether the material 

 was inoculated on the bucco-pharyngeal mucous membrane or on the comb. 



[G. Dean and Marshall have recorded an outbreak of diphtheria in the 

 wood pigeon apparently due to a filtrable virus. By painting a filtered 

 (Berkefeld filter) emulsion of a membrane from an infected bird on to the 

 throat of doves they were able to reproduce the disease experimentally.] 



