TRACHEOTOMY TUBES OK CANNULiE. 



455 



constructed a jointed tube said to be adapted to every form of neck (Figs. 

 359 and 360), but one of the halves sometimes becomes detached and drops 

 into the trachea. Modern experience shows that the tracheal tubes of 



Fig. 359. — Leblanc's jointed cannula. 



Field, Peuch, Jones, and Coleman, which correspond in principle, are 

 amongst the best (Figs. 361 to 363). They consist of two or three pieces, 

 which are inserted singly by first pushing the wider tube into the trachea 

 and afterwards the narrower one, so that the projections point upwards 



Fig. 360. — Leblanc's jointed cannula. 



and downwards in the lumen of the trachea without pressing on its mucous 

 membrane. Provided it is sufficiently long to enter easily, the tube with 

 the shortest projections is to be preferred, because its hold is more secure 

 and is less liable to injure the posterior wall of the trachea. Naturally, 

 the length of the cannula, that is, the distance between the plate and the 



