ANIMAL PATHOLOGY. 
tube seems to possess*', bestowing power on the ligamento-mus- 
cular substance interposed between the rings of the windpipe, 
and governing the flexibility and variety of motion of which this 
elastic tube is susceptible. They likewise give power to that 
transverse muscle which is the tie that prevents the arch of the 
trachea from spurring out when pressure is made upon its crown ; 
and which also secures the windpipe from laceration and rupture, 
when, in the utmost exertion of the animal’s speed, and some- 
times the diseased excitation of the respiratory organs, the cur- 
rent of air rushes furiously along. Finally, it may be by the 
influence of the recurrent branch that the transverse muscle is 
enabled to regulate the smoothness or the corrugation of the 
lining membrane of the windpipe, in accordance with the volume 
of the current, or the irritability of other surfaces over which it 
has to pass. 
The ( Esophctgean Brattches . — As the right recurrent nerve 
ascends the neck, it distributes several branches on the oeso- 
phagus, bestowing on its muscular coat the pow r er of contraction, 
and on the internal lining coat that of sensation. Experiments 
have proved this beyond the shadow of a doubt. By the action 
of the glosso-pharyngeal nerve the masticated food passes through 
the pharynx, and is forced into the oesophagus ; and food being 
* Many circumstances connected with the presence of foreign bodies in 
the trachea, or their occasional passage through it, would lead us to believe 
that there is not that exquisite sensibility of the lining membrane which some 
have imagined. The rimae glottidis are watchful guardians to prevent the 
ingress of that which would be hurtful ; yet their sensibility has probably 
been over-estimated. A probe has occasionally been passed from the pha- 
rynx to the bifurcation of the trachea, without any great degree of suffering 
being expressed by the animal. M. Braschet, in a work on the Ganglionic 
Nervous System, which ought to be in the hands of every veterinarian who 
understands the French language, — he would be rendering the medical and 
the veterinary professions a service who would favour us with an English 
translation of it — proves very clearly that the sensibility of the trachea, in 
whatever degree it may exist, is derived from the great spinal organic nerve. 
He effected an opening into the trachea, immediately below the larynx, ex- 
cising a portion of the cartilage of the trachea : he then divided these 
nerves. The breathing was necessarily much impeded and disturbed, and 
was carried on through this aperture, the glottis having closed. He then 
introduced a little smooth hall of orris-root into the opening, with a thread 
attached to it, and this ascended and descended with every act of expiration 
and inspiration, without the dog seeming to experience the slightest pain. He 
then withdrew the ball, and held a vessel containing muriatic acid close to 
the aperture. This was continued during several minutes, and some portion 
of the gas was of necessity inhaled. No pain or inconvenience was expressed. 
A few drops of the acid were then introduced into the trachea ; but there was 
no expression of pain. Acetic acid was afterwards used; hut the animal 
stirred not. These experiments proved to demonstration that the sensibility 
of the trachea, and of the bronchi too, depended on these nerves, and was 
altogether lost when they were divided. 
