

HUMAN ANATOMY. 



dorsal branches, which are small and irregular. There are usually four large and well- 

 marked ventral secondary bronchi, besides one or two insignificant ones the nature 

 <.f which is not easily determined. The ventral bronchi describe a spiral course 

 thruu.'h the lung, curving forward and inward as they descend, so as to be in the 

 main parallel with the chief fissure. The dorsal branches, running backward, inward, 

 and downward, are not more than four in number, and may be reduced to two. 1 here 

 are two bronchial tubes besides those mentioned above : one, the apical bronchus, 

 supplies the upper part of the lung, on the right springing from the primary bronchus 

 2 cm. or less from its origin. It is a large branch, about 10 mm. in diameter, running 

 upward and outward, and divides into three branches, one of which ascends and two 

 of which run downward and outward on the front and back respectively. It is really 

 the first dorsal branch of the right primary bronchus, but we have not included it in 

 the dorsal branches. On the left the apical bronchus, which closely resembles the 

 right one, but is rather smaller, rises from the first ventral bronchus, of which it 

 may be called a dorsal branch. The other secondary bronchus, not included in the 

 foregoing scheme, is the subcardiac bronchus, which on the right arises usually from 

 the main trunk between the first and second ventral bronchi, or from the second 



ventral bronchus. It 



FIG. 1570. runs downward and 



inward to the region 

 in front of the hi- 

 lum and above the 

 lower border of the 

 lung, which may be 

 marked off as a sep- 

 arate lobe, held to 

 represent the cardiac 

 lobe of mammals. 

 On the left the cor- 

 responding bronchus 

 arises always from 

 the second ventral 

 branch. 



Homologies of the 

 Bronchi. We are in- 

 debted to Aeby l for the 

 idea, now practically 

 universally accepted, 

 that there is a main or 

 primary bronchus ex- 

 tending through the 



lung and giving off both ventral and dorsal branches. After the bifurcation of the pulmonary 

 artery, each of its subdivisions reaches the front of the primary bronchus of each lung, and 

 nling to Aeby) crosses over it so as to lie behind it. This alleged crossing occurs on the 

 right jus! .ittrr the origin of the apical bronchus, which is said, therefore, to be above the cross- 

 ing, and is called by Achy the cpartcrial bronchus. Thus on the right all but one of the branches, 

 .ind mi the left all, without exception, art- given off below the crossing, and are called hypartcrial 

 bronchi. Aehy attached so much importance to this relation that he considered the little irregu- 

 lar middle lobe of the right lung, because it is supplied by the first hyparterial bronchus, the 

 ,.-utati\e of tin- left upper lolie, the right upper lobe being without a mate and the two 

 l.ib.-^ lioinolng. .11-,. It is difficult to understand why such a relation should be of so great 

 2 refutaio o eb o - oar arter is 



Relations of bronchial tree to posterior thoracic wall, as shown by X-rays. 

 (After Blake.) 



given 

 The 



, 

 ling. aa se .i, . a e so-e eparterial apical roncus o e 



nt in the left, arising from the first ventral instead of the primary bronchus. It is a t 

 tiiry bronchus from the first ventral which, especially on the right, is (among mammals) giv 

 SO that it m. iv spring from the main bronchus or even from the trachea. T 

 arterial relation he considers of no importance. Huntington, 3 after much work on human 

 and m mini. ill. in lung-. < ann- to somewhat similar conclusions. He believes that the primary 

 type among mammals i-, ,,ne u jth a hyparlerial bronchus on both sides, and the furthest 



1 I >er r.r..nchialb.mm der Saiigethiere und des Menschen, 1880. 



1 Yerh.tndl. !. Anat. GesellscHaft, 1892. 



* Annals of the New York Academy of Sciences, 1898. 



