THE BRONCHI. 541 



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

 inner surface of the rings, this layer disappears in the smallest bronchial tubes. 



3Iui'ous membrane. — This membrane is distinguished from that of the trachea 

 by its great sensitiveness ; it alone constitutes the 

 walls of the terminal bronchial divisions. (When the ^'g- 321. 



cartilages terminate, the tubes are wholly mem- 

 branous, and the fibrous coat and longitudinal elastic 

 fibres are continued into the ultimate ramifications of 

 the bronchi. The muscular coat is disposed in the 

 form of a continuous layer of annular fibres, and 

 may be traced upon the smallest tubes ; it is com- 

 posed of the unstriped variety of muscular fibre.) 



Vessels and nerves. — The vessels and nerves dis- 

 tributed in the tissue of the bronchial tubes, come 

 from the satellite vessels and nerves of these tubes „,,„„,,„ 



, , , . , . . ^ ^, MUCOUS MEMBRANE OF A BRON- 



— the bronchial arteries, veins, and nerves. The chial tube, with the oapil- 

 lymphatics pass to the bronchial glands. laries injected. 



Differential Characters in the Air-tube succeeding the Nasal Cavities in the 

 OTHER Animals. 



Ruminants.— In the Ox, Sheep, and Goat, the interior of the larynx is simpler than in 

 the Horse, and the lateral ventricles and vocal cords are almost effaced. The most important 

 differences in its various pieces are a.s follows: 1. The thyroid cartilage has no anterior 

 appendices, but is provided, posteriorly, with two considerable prolongations that articulate 

 with the cricord cartilage (it has no excavation between the two wings, and is formed by a 

 single piece : its inner face, in the middle, near the lower border, has a small fossette to which 

 a round and very salient tuberosity on the external face corresponds). 2. The upper border of 

 the cricoid is not notched in front (neither is the bezel on its lower border). 3. The epiglottis 

 is wider, but not so pointed, than in Solipeds (Leyh says it is less extensive, but thicker). 

 4 A hypo-epiglottidean muscle bifid at its origin. (There is no arytseuo-epiglottidean 

 ligament.) 



The trachea of these animals does not offer any important differences. The last ring is not 

 so developed as in tlie Horse, and tlie tube detaches a supplementary bronchus to a lobe of the 

 lung which does not exist in Solipeds. (The rings of the mid<lle portion are proportionately 

 narrow, and their extremities meet behind and form a salient ridge.) 



In the Camel, the larynx is long and flattened before and behind, and the epiglottis is very 

 developed; the entrance to the larynx is triangular in shape, but its borders are convex 

 inwardly. In Ruminants there are some closed fuUicles at the base of the epiglottis. 



Pig. — The larynx of the Pig is remarkable for its great mobility, suspended as it is to the 

 hyoid cornua by the base of a very developed epiglottis, rather than by the wings of the thyroid 

 cartilage. The epiglottis is in shape like an omega, is very high, and curved backwards in 

 such a fashion as to envelop the arytsenoids. There are wide, shallow, lateral ventricles, which 

 have a small oblong sinus that ascends between the thyroid cartilage and the mucous 

 membrane. These ventricles are not surrounded by the thyro-arytsenoideus muscle, which is 

 small and undivided; above and outwardly, tliey are margined by a thick cord — a kind of 

 superior vocal cord, considered by Duges as acting with the ventricles to modify the deep 

 grunting sounds. (Instead of a tuberosity on the external face of the thyroid cartilage, there 

 is a median crest, and its inferior border has a small point. The cricoid appears to be drawn 

 downwards and backwards, and its lower border is very prominent in the middle, and articu- 

 lates with one or two small cartilaginous plates which have been sometimes wrongly described 

 as belonging to the proper cartilages of the larynx. Tlie antero-sup(-rior angles of the arytse- 

 noid cartilages are united to a small cartilaginous piece which prolongs them ; their external 

 face has a spine, and the internal angles are separated by a small pisiform body called the 

 " interarticular cartilage.") 



The trachea of this animal resembles that of Ruminants. (It has about thirty rings, and 

 has three bronchi.) 



Cabnivora.— The larynx of the Dog and Cat is very like that of the Horse. In propor- 

 87 



