MORPHOLOGICAL STUDY OF TRACHEAL AND BRONCHIAL CARTILAGES. 



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the trachea and bronchi of a week-old child (fig. 1), but was later transferred to the 

 guinea-pig, the latter having a smaller trachea and lung. 



It must be understood from the first that animals of different species do not 

 have the same form of cartilage in similar positions and that no two individuals of 

 the same species have exactly the same form and arrangement of the cartilages. 

 This point is well brought out in the studies of the cartilages of the carina tracheae 

 above mentioned. The last eight cartilages of the human trachea and the last five 

 cartilages of the trachea of the guinea-pig were modeled. In each case it was found 

 that only about one-half of the first of the cartilages entered into the model. 



The outline of a transverse section of the trachea and of the cartilage in each 

 of the models does not have the elongated horse-shoe shape of the figure given by 

 Kolliker, or the flattened horse-shoe shape of the figure given by Sobotta; it is 

 more nearly circular (figs. 2 and 5) . As the carina is approached, the posterior mem- 

 branous portion of the trachea flattens and eventually the section has an elongated 

 oval outline ; or it may even have, as is the case with the human trachea, a dumb- 

 bell shape (fig. 3) before it divides into the right and left bronchus. 



FIG. 2. Outline of the section along 

 the line A, in figure 1. Note cir- 

 cular outline of the section. The 

 numbers 2, 3, 4 indicate the carti- 

 lages through which the plane of the 

 section passes. X6. 



FIG. 3. Outline of the section along the line B in figure 1 . 

 Note the outline of the lumen of the trachea ; it has 

 notonly adurab-bell shape, but, there is also a marked 

 anterior swing of what is to be the right bronchus. 

 1 B, section of the first right bronchial cartilage; 

 C, C, sections of the carinal cartilage. X6. 



HUMAN TRACHEA AND BRONCHI. 



Trachea. The cartilages of the human trachea present marked irregularities 

 (fig. 1). The first of the cartilages is incomplete and must therefore be left out 

 of the account; the two following cartilages are regular in their formation; the 

 next five are either fused cartilages or are bifurcated, and have one or more irregular 

 openings, evidently due to incomplete development, for they give passage to neither 

 blood-vessels, nerves, nor gland ducts. The carinal cartilage is interesting, being 

 formed by the fusion of tracheal and left bronchial cartilages (fig. 4) ; both elements 

 present bifurcations and irregularities of outline. 



Right bronchial cartilages. The first bronchial cartilage on the right side con- 

 sists of two elements which fuse as they arch around the mesial side of the bronchus. 

 The next cartilage is a typical crescent. Immediately below this cartilage the 

 eparterial bronchus is given off, and the cartilage placed at this point has a com- 

 plicated structure, part of it belonging to the eparterial bronchus and part of it 

 to the main stem bronchus. The portion belonging to the eparterial bronchus 



