]^32 Atelectasis of the Lungs. 



slaughtering house, found 15% of the slauglitered young pigs affected; 

 50% of sucking pigs; 7% of young goats; sucking calves, 13% ; young 

 sheep, 16%. Atelectasis may be primary or congenital, or secondary 

 and acquired. Congenital atelectasis is due to the fact that portions of 

 the lung do not expand after birth and remain airless during extra- 

 uterine life. Acquired atelectasis occurs if some bronchi become im- 

 pervious (obstruction atelectasis) or if portions of the lung become 

 pressed upon (compression atelectasis). In both cases the air is ab- 

 sorbed within a few hours and the portions affected become void of air. 

 As a third form we may mention marantic atelectasis which also is due 

 to a gradual absorption of the air out of the alveoli. Simader believes 

 that atelectasis in food animals is a congenital affection. 



The cause of congenital and marantic atelectasis is usually an 

 atrophic condition of the respiratory muscles due to fatty degeneration, 

 lack of development, or due to various diseases of infancy (dysentery, 

 polyarthritis, rachitis, rheumatism) ; not uncommonly atelectasis can be 

 referred to insufficient physical exercise if the animals are kept con- 

 tinually in the barn. Obstruction atelectasis usually occurs during 

 bronchial catarrh, more rarely in new-born animals, in consequence of 

 the obstruction of bronchioles by epithelial plugs, by mucus or by 

 aspirated meconium. Compression atelectasis is usually caused by an 

 accumulation of fluids or air in the pleural cavity, more rarely by 

 voluminous tumors of the lungs or pleura. 



Anatomical Changes. The seat of atelectasis is usually in the 

 upper portions especially the anterior lobes of the lungs. The atelectatic 

 foci appear browned, sunken in under the surface of the lungs and 

 wedge-shaped if they are due to a bronchial obstruction. Congenital 

 atelectasis is characterized by its typical location in the apices, by a 

 normal appearance of all bronchi, or at least of those in the neighbor- 

 hood of the atelectatic focus, and also by the fact that the pleural 

 covering does not appear folded. If a portion of lung has not been 

 expanded properly, hyperemia occurs and soon a serous infiltration of 

 the atelectatic focus (splenization) develops; the epithelia then undergo 

 fatty degeneration and become desquamated; mucoid material collects 

 in the bronchioles and leucocytes wander into the interstitial connective 

 tissue (desquamative catarrh). The tissue elements which have under- 

 gone fatty degeneration are absorbed and this is followed by marked 

 atrophy which may progress to a degree that the two opposite leaves 

 of the pleura finally touch (induratio). 



There exist no observations concerning the clinical symptoms. It 

 is, however, proliable that in extensive atelectasis disturbances of respira- 

 tion and physical changes in the thoracic sounds may be found similar 

 to those encountered in catarrhal pneumonia. Congenital pulmonary 

 atelectasis must always be suspected when animals are apparently still- 

 born. Atelectatic foci of lesser extent do not cause any symptoms at all. 



The significance of the lesion depends upon the underlying cause. 

 Atelectasis is of a certain importance because it might be confounded 

 with contagious bronchopneumonia of young animals and an inflam- 

 matory process may be established secondarily in the atelectatic focus 

 (usually bronchopneumonia, exceptionally croupous pneumonia), due 

 to the action of non-speciflc microorganisms. Specific microorganisms 

 may sometimes invade an atelectatic focus. (Hogs develop the pneu- 

 monic t.ype of hog cholera in this way.) 



The treatment of acc|uired atelectasis depends upon the cause. 

 In congenital atelectasis one must attempt to stimulate respiration by 



