DIFFERENTIAL DIAGNOSIS 155 
the disease starts at the head or toes. Since mange may, 
however, occur simultaneously with a distemper eruption, 
a diagnosis would be rendered definite upon the search 
for and demonstration of the causal parasites of mange. 
To state precisely whether one is dealing with dis- 
temper in its early stages or with a simple non-specific 
catarrh is a matter of impossibility, since distemper so 
frequently appears at its onset as a disease of perhaps 
only one organ, such as bronchitis or rhinitis, etc. The 
previous history—if any—would have to be taken care- 
fully into account as before mentioned, after which we 
would need to await the development of some confirma- 
tory symptom, or microscopically examine the nasal 
discharge (if any) or a swab from the pharynx or larynx, 
for the purpose of demonstrating the presence of 
B. bronchisepticus—assuming this organism to be capable 
of setting up true distemper. 
