PATHOLOGY OF PULMONARY DISEASES OF THE HORSE. 
21 
tion muscles, and the more or less complete obstruction of the 
respiratory way, would therefore decide the extent of atelectasis. 
Have single inspiration muscles suffered pathic changes of an 
inferior grade ? then the respiration is only partially disturbed. 
The lungs are then only atelectatic here and there. Or, are only 
individual bronchi obstructed, that is, the connective-tube is only 
partially obstructed ? then the atelectasis would only come to 
observation in those parts of the lungs to which the bronchi in 
question lead. We find the obstruction of single bronchi by con¬ 
genital bronchitis catarrhalis. I have to the present time met 
with bronchitis congenitalis only by calves, and would infer (with 
Frank) that the aspiration of the liquor amnii may be looked upon 
as the cause of the same. Every bronchitis gives a secrete. The 
number of diseased bronchi may vary, and corresponding to the 
same would be the extent and number which would be obstructed. 
The atelectasis following bronchitis is not alone conditioned by 
the secretory products, mucous, pus, etc., but other circumstances 
all aid in producing it. Every irritation of a mucous membrane 
causes tumefaction of the same, and this swelling is of itself suf¬ 
ficient to obstruct the lumen of very narrow canals lined with a 
mucous membrane. Further, the functional capability of the 
respiration muscles is of importance. When the respiratory 
forces are sufficient to cause the extension of the thorax of a new 
born animal, then the hindernesses to the respiration caused by 
the catarrh may be overcome, by the powerful respiration. By a 
weak animal, however, the musculature of which is but poorly 
developed, poorly nourished, or has suffered pathic metamorpho¬ 
ses, that is, one by which the act of respiration is but weakly 
executed, the obstructions of the bronchi cannot be overcome. It 
is by such animals especially, that the lungs remain to a greater 
or less extent in a foetal condition. The last is known as congen¬ 
ital atelectasis. Congenital atelectasis was for a long time looked 
upon as a congenital form of pneumonia. Jorg was the first to 
correctly consider the atelectatic condition of the lungs and to 
recognize the same as the result of an insufficient filling of the 
alveoloe with air. 
Against this congenital form of atelectasis we have the acquired. 
