MORPHOLOGICAL STUDY OF TRACHEAL AND BRONCHIAL CARTILAGES. 293 



This element is in the form of an elongated cap which incloses nearly three- 

 fourths of the circumference of the bronchus and extends from the point where 

 it leaves the right bronchus to the point where the apical branch arises. On the 

 ventral side of the cartilage three deep notches and a single opening are seen; 

 none of them gives passage to either blood-vessels, nerves, or glands. On the dorsal 

 side is a deep notch which ends in a crescentic bay that gives passage to blood- 

 vessels; the lateral margin is irregular, and the entire dorsal surface slopes toward 

 the broncliial element with which it eventually fuses. 



The second of the large cartilages associated with the eparterial bronchus 

 belongs essentially to the main stem bronchus. In a ventral view (fig. 12) it ap- 

 pears as a band, placed transversely across the long axis of the stem bronchus, 

 with a prolongation springing from its lateral margin which bears a slight re- 

 semblance to the bow of a ship and supports the eparterial bronchus in a manner 

 somewhat similar to that by which the bowsprit of a ship is supported by the 

 bow. In a dorsal view (figs. 13 and 16) this resemblance is not as pronounced as 

 in the ventral view; this is due to a slight dorsal swing of the eparterial bronchus. 



FIG. 10. Outline of section taken along the line indicated in figure 12. R. B., right bronchus. 

 L. B., left bronchus. R.I. m., bronchus to right lobus medius. L.I. a., bronchus to 

 left lobus anterior. The relation of the various pieces to the complete cartilages can 

 be made out without difficulty. X6. 



The dorsal view also shows the close approximation of the two extremities of the 

 cartilage, a foramen for the passage of a small branch of the bronchial artery 

 and a small hook-line process arising from the posterior border of the lateral end 

 of the cartilage. 



The relation of these two cartilages to the eparterial bronchus is best shown 

 in a view taken dorso-laterally (fig. 17). Here the capping of the eparterial 

 bronchus by the first cartilage and the bracing of the bronchus by the second 

 cartilage are clearly brought out. The relation of the second cartilage to the epar- 

 terial bronchus is also shown in the outline of a section taken through the anterior 

 portion of the cartilage (fig. 7). This section also shows the position of the sections 

 of the cartilages belonging to the left bronchus. 



A longitudinal section (fig. 8) of the greater part of the eparterial bronchus 

 before it breaks up into its principal branches shows the position of the various 

 cartilages found along its course. The most interesting cartilage is the one that 

 nearly surrounds the first of the small branches which arises from the dorsal side 

 of the bronchus. It is shown in figure 8 in section, and in figure 13 it is shown 

 reconstructed. This cartilage belongs primarily to the first dorsal branch; it also 

 is the main cartilage associated with the second dorsal branch. The first branch 

 takes a dorso-mesial direction, while the second branch takes a slightly dorso- 



