222 DISEASES OF THE AIR-PASSAGES OF HORSES. 
rally attended by patches and lines of inflammation of the mucous 
surface. 
iMembraniform Concretions. —These formations, commonly termed 
false membranes, but, in fact, having no claim to the appellation of 
membrane in its true sense, in any degree, are found upon the in¬ 
ner surface of the air-passages more frequently than any other mu¬ 
cous duct. It has been considered by some pathologists that these 
animal planes are the product of a high degree of inflammatory 
action : this I conceive an error, and should rather attribute them to 
an excess of albuminous principle in the blood, united with a dispo¬ 
sition in the secretory vessels to discharge it. These concretions 
are rarely, if ever, organised, and in substance and consistence, in 
cases, vary from situation, together with other circumstances. Their 
conformation differs: the deposition may take place in patches, 
membranous bands, traversing the canal in layers, or even perfect 
tubes, or formed like a polypus. Fortunately, these membraniform 
concretions do not often occur: I enumerate them only as changes 
to which the mucous membrane of the air-passages is subject; 
however, cases of roaring, fatal dyspnoea, and death, have been 
produced by them. Worms are sometimes found in the air-tubes, 
more especially in cattle ; but their existence in this situation arises 
from a source differing from and independent of alterations of any 
of the structures composing the air-tubes, therefore a descriptive 
history of them is not connected with the present subject. 
Hemorrhage from the Mucous Membrane is an occurrence to be 
enumerated as another change or lesion of the respiratory surface, 
and may take place during the existence or absence of the ulcera¬ 
tion or breach of the membrane: it rarely occurs to an extent 
sufficient to destroy life. I never saw death happen from this 
accident, and the lesion confined to the membrane; but blood is 
frequently found in the respiratory canal, in animals that have died 
with diseases of the heart or lungs, extravasated underneath the 
mucous surface in coagulated patches, various in extent and situ¬ 
ation, to Avhich is given the term ecchymoma or ecchymosis. 
The fibrous and muscidar Sty'uctures undergo abnormal changes: 
softening or hypertrophy of the fibrous tissue of the bronchi is 
sometimes observed; the ligaments of the glottis become softened, 
lose their natural colour, and even change to cellular-like or lea¬ 
ther-like tissue : occasionally these ligaments, as also those of the 
trachea, are absorbed, and give rise to adhesions of some of the 
cartilages. The muscular structure, as entering into the formation 
of the trachea, as well as the muscles of the larynx, may be either 
atrophied or hypertrophied, softened, and partially destroyed by 
ulceration. The laryngeal muscles are sometimes hypertrophied 
