TRACHEOTOMY TUBES OR CANNULAS. 



457 



in making cannula? on Peuch's model. These seem to be well suited for 

 race-horses. Where it is necessary to combat suffocation occurring in 

 purpura and other diseases, a cannula of a long form is selected, in order 

 to avoid bruising the tissues at the point of operation. In anticipation 

 of swelling supervening, the steadying of the cannula may be effected by 



Fig. 363.— Coleman's tracheotomy tube. 



placing one or more leather shields below the plate, or enveloping the 

 projecting portion of the tube in gauze or tow. 



The tube gradually becomes stopped by secretion from the mucous 



Double- tube cannula. 



membrane, and must, therefore, be frequently cleansed, at first indeed, 

 daily. As the secretion diminishes cleansing is only required at intervals 

 of a week or ten days, and afterwards the tube should be disturbed as 

 seldom as possible. It is advisable, however, to have two similar cannula?, 

 so that whilst one is^in use, the other can be cleansed or, if need be, repaired. 

 Such precautions are necessary, because the wound contracts very rapidly ; 



