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MORPHOLOGICAL STUDY OF TRACHEAL AND BRONCHIAL CARTILAGES. 



has a prolongation which is associated with a small bronchus, arising from the 

 eparterial bronchus, which is not shown in the outline. Three openings are 

 present in the main portion of the cartilage which are probably due to incom- 

 plete development. From the description given by Horner and by King, a cartilage 

 should be present in the angle formed by the eparterial bronchus and the main 

 stem bronchus, having more or less of a saddle shape with the concave surface 

 uppermost; but, as is the casein the guinea-pig, quite another type of cartilage is 

 present. 



Left bronchial cartilages. On the left side the cartilages were not followed 

 out completely, but, as far as they were followed, they formed a single fused 

 cartilage made up of several elements, with numerous openings which, like those 

 mentioned above, did not give passage to either blood-vessels, nerves, or gland 

 ducts. 



FIG. 4. Reconstruction of the carinal cartilage shown in outline in figure 1. A, anterior view; B, poste- 

 rior view. Note the extensive fusion of trachea and bronchial elements. This belongs to what 

 is known as the " tracheo-bronchial left" type of carinal cartilage. X6. 



The study by Heller and v. Schrotter, taken in connection with the study 

 made by Miller, seems to indicate that the cartilages of the trachea and of the 

 right and left bronchus in man are subject to a greater number of fusions and 

 bizzare forms than is the case in the lower mammals; a more extended study of 

 the lower forms might, however, prove this conclusion to be erroneous. 



GUINEA-PIG. 



The cartilages of the trachea and bronchi will be described first as they appear 

 in a ventral view (fig. 12), and then as they appear in a dorsal view (fig. 13). The 

 one shows what may be termed the bodies of the cartilages, the other, the ends 

 of the cartilages. 



Trachea. In contradistinction to the human trachea, that of the guinea-pig 

 presents no marked irregularities. The last tracheal cartilage has the triangular 

 prolongation downward that is described as characteristic of this cartilage, but it 

 does not enter into the carina tracheae, the carinal cartilage being the first cartilage 

 of the left bronchus. 



