456 JOINTED TRACHEOTOMY TUBES. 



curvature of the projections, must correspond to the thickness of the anterior 

 wall of the neck. Such tubes may be worn by horses for several years 

 without producing stenosis or difficulty in application. Hauptner has 

 recently somewhat modified Peuch's tube. The inner portion is made 

 lighter and can be more easily introduced ; but, on the other hand, it has 

 not so wide a basis, and, therefore, more easily produces proliferations. 

 To introduce the tube the index finger of the left hand should first be 



Fig. 361.— Peuch's cannula. 



passed into the trachea, when the first limb of the tube may easily be slid 

 along it, the finger acting as a guide. Afterwards the second portion is 

 inserted. 



Field's tube is largely used in England, and is convenient to insert 



Fig. 362. — Field's tracheotomy tube. 



and withdraw as well as to clean. The shields and half tubes should, 

 however, be either in one piece or be very securely welded in order to 

 prevent accidents. 



Coleman's tube is also to be recommended as light, simple, and con- 

 venient. The parts are very firmly united when the tube is in position, 

 and there is less danger of their being displaced by the patient than in the 

 case of Field's tube. 



Cannulas must be light and durable, and their edges, as already stated, 

 well rounded off. They are usually made of German silver, but their 

 weight may be reduced by using aluminium, which has been employed 



