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Following the nomenclature of Heller and v. Schrötter the 

 carina tracheae of the cat may be arranged under the following types, 

 viz., tracheal ; tracheo-bronchial right ; tracheo-bronchial left; bronchial 

 right; bronchial left; double bronchial; mixed; membranous. 



Tracheal: The last tracheal ring is provided with an elongated 

 spur on its lower border which projects downwards and enters the 

 dividing ridge between the right and left bronchus (Fig. 1). In the 

 cat the tracheal type differs from that in man in that the spur is not 

 so long and narrow, neither does it project as far into the carina. A 

 sharp distinction exists between this type and that described below as 

 "mixed". Sometimes the last two or three tracheal rings are fused 

 more or less completely, but it is always the last element that bears 

 the spur. 



Tracheo-bronchial right: This type is formed by the fusion 

 of the last tracheal cartilage with the first bronchial cartilages on the 

 right side. In some cases (Fig. 2) this fusion is quite extensive. 



In the following figures the cartilages are represented by solid black bands. Each 

 figure shows the trachea and bronchi cut open and viewed from behind. 



Fig. 1. Tracheal type of the carina. The last tracheal ring bears a triangular 

 spur which enters the carina. The first three cartilages of the right bronchus are fused 

 at their mesial end. 



Fig. 2. Tracheo-bronchial right. An extensive fusion has taken place between the 

 last two tracheal and the first two bronchial cartilages. 



Fig. 3. Tracheo-bronchial left. The last tracheal and the first two cartilages of 

 the left bronchus have fused along their mesial border into a plate of cartilage which 

 enters the carina. 



Tracheo-bronchial left: This is formed by the fusion of 

 the last tracheal cartilage with the first bronchial cartilage on the left 

 side (Fig. 3) and like the preceding type the fusion often includes 

 several cartilages. 



Bronchial right: The cartilage which enters the carina in 

 this type is derived from the first right bronchial cartilage (Fig. 4). 

 The last tracheal ring may or may not have a slight spur; if such is 

 the case it fails to reach the carina. 



