1 68 ' Veterinary Medicine. 



found the upper rings completely flattened upon themselves from 

 side to side, so that it was impossible that breathing should be 

 established. 



Detachment and wide separation of the free ends of 

 the tracheal rings, I found in an old horse used for dissect- 

 ing purposes. The space between the detached ends was suf- 

 ficiently capacious to hold the cesophagus, with its attached nerves, 

 vessels and lymphatics. Goubaud quotes a similar case, Cadeac 

 one in which the ends of the rings were nearly four inches apart, 

 and Vegezzi one in which the intervening space lodged the gul- 

 let, vagus and sympathetic nerves, and the carotid artery. In 

 such cases it appears as if the tracheal ligament between the free 

 ends of the rings were torn and the trachealis muscle detached 

 from the outer free end for a considerable distance. The lumen 

 of the trachea is invariably narrowed in its supero-inferior diame- 

 ter, and the volume of air admitted must have been materially 

 reduced. 



Flattening of the trachea supero-inferiorly is usually 

 the result of external pressure, and all flattening, causing as 

 it does a deviation from the strictly circular outline, diminishes 

 the calibre of the tube and its conducting power. Old horses 

 with ewe-necks are especially subject to this disortion, from pres- 

 sure of the vertebrae and their investing muscles. A sacculated 

 cesophagus may be another cause, also tumors or phlegmons sit- 

 uated above the trachea (adenoma, melanoma, actinomycosis, 

 strangles). Cadeac records a case of lateral flattening of the 

 lower end of the trachea. 



Excessive overlapping of the free ends of the rings 

 is noted by Blaise, the rings appearing rolled on themselves 

 around a narrow opening. 



Thickening of the submucosa with constriction of the lu- 

 men is described by Lepper. 



Elongated and tortuous trachea with successive devia- 

 ' tions to the right and left are vouched for by Baldoni and Johne. 



DISTORTIONS OF TRACHEA IN DOGS. 



Much less common than in the horse, these are mostly due to 

 goitres or to enchondroma, tubercle or epithelioma of the thy- 

 roid (Cadeac) or to other neoplasms along the course of the windr 

 pipe. 



