DEPARTMENT OF SURGERY. 
699 
_ 
muni by the use of a new tracheotomy tube devised for this 
purpose by Dr. M. H. McKillip. The advantages of its use 
have been carefully observed ; and besides preventing tracheal 
deformities, its use has verified that it is more easily applied 
than any other tracheotomy tube in general use. The tube is 
elliptical instead of circular. The transverse axis (latus transver- 
suni) of the lumen is 25 mm. in length, and its congugate axis, 
about 12 or 13 mm. The length and direction is the same as that 
of any ordinary curved tracheotomy tube. A tube with these di¬ 
mensions can be inserted into the trachea without destroying or 
removing any cartiliginous tissue. The condition following 
tracheotomy is generally irreparable ; the trachea will either 
collapse or dilate, which impairs the respiratory function and re¬ 
duces the value and usefulness of the animal. Stenosis and 
collapse of the trachea are the most serious conditions following 
the operation, when the cartilages are incised or part of them 
excised. When the cartilages are incised and the tube inserted 
without excising part of them, the strain brought upon the 
lateral arcs (Fig. 36-Aa) of the cartilaginous rings caused by 
spreading them apart to form an aperture for the tube, encour¬ 
ages softening and absorption of the cartilaginous tissue forming 
these arcs ; and as a consequence, the curvature is replaced by 
a straight cartilaginous wall or even a convexity (Fig. 36-B), 
which reduces the calibre of the trachea when the tube is re¬ 
moved and the cartilages are approximated. When the tube 
FIG. 36. 
A, abnormal tracheal ring; a, lateral arcs ; b, segment removed in tracheotomy ; c, trache- 
, ® muscle. B, Collapse of tracheal -ring ; C, collapse of ring with convexity in lumen ; a, col¬ 
lapse resulting from softening of arcs. 
