////: Til. If UK A. 461 



Form. Tho bronchial tubes arc not flattened liko the trachea; a 

 transverse section shows them to be regularly cylindrical. 



Volume. The left bronchus is always smaller than the right, and both 

 are much inferior in volume to the aggregate of their respective branches. 



Relation*. Each bronchus enters the pulmonary lobe along with the 

 blood-vessels, which with it forms what is called the root of the lung. Tho 

 divisions of this arborescent trunk are accompanied by the bronchial artery, 

 vein, and nerves, which ramify in the same manner. 



Near their origin, the bronchi are related to the bronchial glands, above 

 which, and to the left side, passes the oesophagus. 



STRUCTURE The structure of the bronchial tubes resembles that of the 

 trachea ; their walls being formed by a cartilaginous framework, a muscular 

 layer, mucous membrane, and vessels and nerves. 



Cartilages of the bronchi. Tlicse only exist in tubes of a certain calibre, 

 the minute passages being deprived of them, and having only membranous 

 walls. As in the trachea, this framework includes, for each tube, a series 

 of transverse rings joined border to border ; though these are no longer 

 formed of a single arciform piece, but each results from the union of several 

 lozenge-shaped pieces whose extremities overlap, and which are united to 

 each other, like the cartilaginous segments of the neighbouring rings, by 

 means of cellular layers, and also by the membranes spread over their 

 internal surface. 



Muscular layer. Extended in a very thin continuous layer over the 

 entire inner surface of the cartilaginous rings, this layer disappears in the 

 smallest bronchial tubes. 



Mucous membrane. This membrane is dis- Fig. 233. 



tinguished from that of the trachea by its great 

 sensibility ; it alone constitutes the walls of 

 the terminal bronchial divisions. (When the 

 cartilages terminate, the tubes are wholly mem- 

 branous, and the fibrous coat and longitudinal 

 clastic fibres arc continued into the ultimate 

 ramifications of the bronchiae. The muscular 

 << 'ut is disposed in the form of a continuous 

 Layer of annular fibres, and may be traced upon 

 the smallest tubes ; it is composed of the un- 

 striped variety of muscular fibre.) 



Vessels and nerves. Tho vascular and ner- 

 vous branches distributed in the tissue of the ** n ' m,T,,r n 



, . - , , ... . < IIIAI. Tilth, WITH "Tilt. CAFIL- 



bronchial tubes conn; from the satellite vessels I.AIMI- 



uinl nerves of these tubes the hrom-Jiinl arteries, 



veins, and nerves. The lywjihutics pass to the bronchial glands. 



DIFFERENTIAL CHARACTER IN THE AIK-Tl BE SUCCEEDING THE NABAI. CAVITIES IN OTHER 



THAN SOLII'EU ANIMALS. 



Ki MivANTS. In the Ox, .s'//7>,and Goat, the interior of tLo l<ir>ins i>Mmpl. r than in 

 til-- II..rsc, and the lateral ventricles ami \.x-.d cords are^lmost efftv-ed. Tin- roost 

 ini|K>rt mt diU'iMvnrj's in its v.irion-; |>i< ' - ure n.s follows: I, Tin- thyroid <\irtila 



no Mtakr ppeodioeo, btrt i-i provided, posteriorly, with tw ...... n i.hr.iMe prolongations 



tli it articulate \\itli tin- criroid cartilai! it has no < \c.t\.iti"ii between tM tWO Wingl, 

 nti'l is t'orinc-tl liy n >ini;li i piicc; its inni-r f.irc, in tin- middle, in nr the ln\vi-r lr<in. 

 Mii;i!l I' >.-. -iti- to which n round and very Milicnt tnlc ro-ity on the r\t< rn il 



i : '1, Tin- npjKTlxirdcr of tin- rricoid i.- not notc|i.-.| in fmnt (neither is tin- ).. 



' : :!. The ej.i-l .1 is is wider, luit los acut". than in S.dii>fds Ix-yh says it 



