SECTION VI 
THE EESPIRATORY SYSTEM AND ITS 
RELATED STRUCTURES 
It is customary to divide the descriptions of normal 
and diseased conditions of the upper entrance to the body 
into respiratory and alimentary parts, the nose, naso- 
pharynx and larynx belonging to the former, the mouth, 
buccal cavity and pharynx to the latter. As a matter of 
fact they can for most purposes be considered as the 
structures contained in the anterior head and furthermore 
their pathological states are more often followed by exten- 
sions into or implications of the respiratory organs 
proper than of the alimentary tract. From a comparative 
standpoint the incidence of specific infectious diseases and 
of the involvement of accessory nasal sinuses present the 
most interesting subjects. There are several infections, 
believed to be specific, observed among domestic mammals 
and birds but their actual individuality has hardly been 
unexceptionally proved. This refers to the communicable 
rhinitis of cows, pigs, rabbits, and birds, especially 
parrots, the follicular catarrh of horses, and croupous 
nasopharyngitis, all of which have been ascribed to a par- 
ticular virus, mthout finished evidence in many instances. 
Some of these diagnoses doubtless cover or are confused 
with the early symptoms and signs of the disease of pro- 
tean manifestations, distemper, and indeed the Bact. 
septicus and relatives of the bird cholera organisms are 
reported as being responsible for them. No intention of 
excluding well recognized entities like bird diphtheria, 
foot and mouth disease or influenza, exists. I shall refer 
below to small groups of epizootics which do not conform 
strictly ^vith word pictures drawm by Hutyra and Marek, 
Moore, or Ward and Gallagher. 
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