CHAPTER III 
ETIOLOGY 
Ultravisible Virus Theory.—As a result of some experi- 
ments carried on by Carré in 1905, and confirmed later 
by Ligniéres (“La Maladie des Chiens,” Bulletin Soc. 
de Med. Vet., 1905), the former became convinced that 
“the specific virus or essential element of the disease is 
invisible, passes through the very porous meshes of the 
bacterial filter, and is not culturable on various media, 
the latter remaining sterile. The most active virus is 
that found in the limpid, serous, or watery nasal dis- 
charge seen in the early stages of the complaint; it is 
equally as virulent when obtained from the pericardial 
effusion after the death of an animal from peracute or 
rapid distemper. The filtered and largely diluted dis- 
charge, or one-hundredth of a cubic centimetre of peri- 
cardial serosity—products not containing any stainable 
or culturable microbe—cause, after three or four days, 
a high elevation of temperature, rapidly reaching 105° or 
more, and lachrymation, followed by coryza, and after- 
wards by a somewhat hoarse cough, especially when the 
animal moves about. At the endof eight orten days, typical 
vesico-pustules appear on the places of their election— 
namely, abdomen and thighs. The lungs become affected ; 
the nasal discharge, at first slight, serous or sero-purulent, 
takes on a purulent character, and continues to flow 
from the nostrils, and the animal dies after a period of 
from one to three weeks.” 
The filterable virus or ultramicroscopic theory thus 
became established, and nearly all authorities still agree 
in ascribing as the direct cause of distemper a specific 
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