1838 



HUMAN ANATOMY. 



the spur on the left of the middle of the trachea in 57 per cent. , in the middle in 42 

 per cent., and on the right of it in the remainder.' Semon, in 100 examinations of 

 the living, found it on the left in 59, at the middle in 35, and on the right in 6. 



The roots of the lungs consist of the bronchi (the right one giving of! a branch 

 before entering the lung), the pulmonary artery and vein, the bronchial arteries and 

 veins, the lymphatic vessels and nodes, 



Fig. 1561. 



Anterior surface Carina, anterior triangle 



Cartila 



and the nerves. 



The bronchi (Fig 1562) are the 

 two tubes into which the windpipe divides, 

 one running downward and outward to 

 each lung. Until they enter the lungs, 

 their shape and structure are precisely 

 those of the trachea, the membranous por- 

 tion being still posterior. This applies also 

 to the branch that springs from the right 

 bronchus before it enters the lung. While 

 treating of the root of the lung we shall 

 consider only the extrapulmonary part of 

 the bronchi. According to modern usage, 

 the term "bronchus" is applied to the 



whole of the chief tube that runs through each lung ; formerly it was restricted to 

 the part from the trachea to the first branch. As the left bronchus gives off no 

 branch before entering the lung, it was described as much longer than the right one. 

 The length of the left bronchus to its first branch is about 5 cm. (2 in.), that of the 

 right is rarely more, and often less' than 2 cm. (^ in.). There are some eight or 

 ten rings in the left bronchus before the branch, while in the right one there are three, 

 often two, and sometimes four. The right bronchus, which is the more direct con- 

 tinuation of the trachea, is the larger. The diameter of the bronchi at their origin is 

 greater from above downward than from before backward. The dimensions are very 

 differently given. According to Aeby, the transverse diameter of the right bronchus 



is from 13. 5-21 mm. and that of the left 



Right apical 

 Left bron'chus y / / broncfius 



Carina tracheae Origin of apical bronchus 



Continuation of right main bronchus 



Bifurcation of trachea, seen from above after section of 

 windpipe just above carina. 



Fig. 1562. 



Membranous 

 part of tra- 

 cheal wall 



from 1 2. 5-1 7 mm. Braune and Stahel 

 found that the calibre of the right one is 

 to that of the left as 100:77.9. The 

 extreme ratios of the series were 100 : 71.6 

 and 100 : 83.3. We have deduced from 

 Heller and v. Schrotter's tables that in 

 some 10 per cent, the calibres are equal. 

 It was formerly taught that the larger 

 right bronchus is more nearly horizontal 

 than the left, but that the contrary is true 

 is easily proved by a glance down the 

 trachea in a frozen section (Fig. 1561). 

 The cause of the error is that, if it be not 

 recognized that after the apparent splitting 

 of the right bronchus the lower division is 

 the main trunk, the eye is apt to follow 

 the upper border of the primitive bron- 

 chus, which carries it along the upper 

 branch. It is very difificult to determine 

 the angles at the origin of the bronchi, 

 for the parts are so flexible that observa- 

 tions on non-hardened subjects are of little 

 value, and it is not easy accurately to measure even good preparations, on account of 

 the irregularity of the oudine. One fact which adds to the difficulty of taking satisfac- 

 tory measurements, and which also tends to make the right bronchus the more direct 

 continuation of the trachea, is the inclination of the latter to the right as it descends. 



' They state that this remainder consists of 8 cases, but as their series comprised 125, it 

 would seem that there must be a misprint. 



Carina 

 tracheae 



Right 

 apical 

 bronchus 



Left bronchus 



Bifurcation of trrchea laid open after incision along an- 

 terior wall of trachea and bronchi. 



