NIXTII ANNUAL YEAR BDOi:— PART X 413 
tlie membrane. pharyna:eal lolyiji. r>foimecl bcr.es. paralysis of the wing 
cf the i.oLtril. et(.. aie occasicnal cau.sj's. The noisy breathing of horses 
afler ha\iiig been idle and put to sudden exertion is not due to any dis- 
la&e and is c:iiy teniiiorary. Veiy o;teu a nervous, excitable horse will 
maUe a noise tcr a slioit ti-ne v\lie:i started off, generally caused by the 
cramped iicsiticn in v. liich the hiad and Leek are lorced in order to 
hold him back. 
I\'any other causes niay rccaMon temporary, intermitting, or permanent 
roisy lespiraticn. hut (hionic icaiing is caused by ])aralysi3 of the 
inisc!es cf the larynx; and almost invariably it is the muscles of the left 
Li^e cf tl.e larynx that aie alTected. 
In chronic tearing the ncise is made when the air is drawn into the 
lun^; and only v\hen the disease is far advanced is a sound produced 
\ he:i the air 13 expelled, and e»eu then it is not near so loud as during 
inspiration. 
In p. normnl condition the muscles dilate the aperture of the larynx 
by moving outward the car'ilage and vocal cord, allowing a sufficient 
Aolunie cf air to rush through. But when the muscles are paralyzed the 
cartilage and \ocal cord that are normally controlled by the affected 
muscles lea-i into the tuLe cf the larynx, eo that when the air rushes in 
it meets this cbstructicn and the noise is produced. When the air is 
expel: ed from the lungs its very force pushes the cartilage and vocal 
cords out, and consequently noise is not produced in the expiratory act. 
The paralysis of the muscles is due to derangement of the nerve that 
supplies them with energy. The muscles of both sides are not supplied 
by the same nerve; there is a right and a left nerve, each supplying its 
respective side. The reason why the muscles on the left side are the 
ones usually paralyzed is owing to the difference in the anatomical ar-t 
rangement of the nerves. The left nerve is much longer and more ex- 
posed to interference than the right nerve. 
In chronic roaring there is no evidence of any disease of the larynx 
other than the wasted condition of the muscles in question. The dis- 
ease of the nerve is generally located far from the larynx. Disease of 
parts contiguous to the nerve along any part of its course may interfere 
with its proper function. Enlargement of lymphatic glands within the 
chest through which the^ nerve passes on its way back to the larynx is 
the most frequent interruption pf Jiervous supply, and consequently roar- 
ing. When roaring becomes confirmed, medical treatment is entirely- 
useless, as it is impossible to restore the wasted muscle and at the time 
remove the cause of the interruption of the nervous supply. Before roar; 
ing becomes permanent the condition may be benefited by a course of 
iodide of potassium, if caused by disease of the lymphatic glands. Elec- 
tricity has been used with indifferent success. Blistering or fireing over 
the larynx is, of course, not worthy of trial if the disease is due to 
interference of the nerve supply. The administration of strychnia (nux 
vomica) on the ground that it is a nerve tonic with the view of stimulat- 
ing the affected muscles is treating only the result of the disease without 
considering the cause, and is therefore useless. The operation of extir- 
