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MORPHOLOGICAL STUDY OF TRACHEAL AND BRONCHIAL CARTILAGES. 



forms two processes below, one of which belongs to each vessel of the division. The 

 free margin of the cartilage, placed at the orifice of an air-tube, is always concave and 

 sharp, and is surmounted by a band of yellow elastic tissue. At the points of origin of the 

 smaller air-tubes, the cartilages exist as thin semilunar pieces, with sharp concave margin 

 looking upwards; these becoming smaller, at length disappear." 



Heller and v. Schrotter studied the car- 

 tilages which enter into the formation of 

 the carina tracheae and, although shown 

 by flat drawings, they indicate better than 

 any previous illustrations the bizarre forms 

 which the tracheal cartilages often assume. 



In a study of the carina tracheae of 

 the domestic cat, made by the author of 

 this paper, a similar method of illustration 

 was used, but while it served the purpose it 

 did not in the end prove satisfactory. 



Schaf er, describing the cartilages within 

 the lungs, says: 



[They] "no longer appear as imperfect 

 rings running only upon the front and lateral 

 surfaces of the air tubes, but are disposed over 

 all sides of the tubes in the form of irregular- 

 shaped plates and incomplete rings of vari- 

 ous sizes. These are most developed at the 

 points of division of the bronchia, where they 

 form a sharp concave ridge projecting inwards 

 into the tube." 



Further quotations are unnecessary, 

 for all the descriptions of the bronchial 

 cartilages seem to have taken their color- 

 ing from the original descriptions given by 

 Homer and by King. No one, however, 

 has followed out the plastic representation 

 of the cartilages first attempted by King. 



In longitudinal sections of the trachea 

 or of the bronchi a considerable number of 

 so-called plates are seen (fig. 10) and it was 

 a desire to see in plastic form the shape and arrangement of these plates that led 

 to the present study. 



Cuvier was the first to point out that the musculature of the trachea in some 

 animals is inserted on the outer surface of the cartilages, in others on the inner 

 surface of the cartilages. This apparently does not influence the shape of the 

 cartilage but it led to the selection, for this study, of the tracheal and bronchial 

 cartilages of man and of the guinea-pig (Cavia cobaya), both of which have the 

 muscle attached on the inner surface of the cartilages. The study was begun on 



FIG. 1. Outline of a reconstruction of the lower portion 

 of the trachea of a week-old child. Only a part of the 

 uppermost cartilage enters into the reconstruction. 

 The lines drawn across the reconstruction show the 

 plane of the sections indicated. Note the angle at 

 the bifurcation, the greater diameter of right bronchus, 

 and that the carina is at left of midline. X6. 



