110 
INTERNAL CANKER, OTORREKEA, OR 
the wound may be painted with tincture of iodine and dusted with iodo¬ 
form. Healing is further assisted by binding the ears close to the head 
with a broad bandage, or by using a net. This disease must be 
distinguished from the next in series. 
(4.) INFLAMMATION OF THE EXTERNAL AUDITORY 
MEATUS (OTITIS EXTERNA). OTORRHCEA. 
This is termed in Germany “ internal canker,” in contradistinction to 
the ulcerative and chronic inflammatory processes of the cartilage of the 
ear, which have been described as “external canker.” To avoid 
mistakes, it would be better to discontinue the use of the terms otitis 
externa and interna. 
The meatus extending from the auditory opening to the tympanic 
membrane has externally a cartilaginous foundation, internally a bony 
one. It is lined by skin, rich in large spherical wax glands. 
Causes. In dogs with long ears, occasionally in other animals, the 
waxy secretion decomposes in consequence of exclusion of air, high 
temperature, and restricted evaporation, and its products irritate the 
lining of the meatus. Inflammation is seldom caused by the entry of 
foreign bodies into the external auditory opening, though Hering has 
met with acan of sarcoptes cynotis, or more properly dermatophagus 
cams. Although examining many dogs suffering from otitis externa 
Holler has never found acari in the external meatus, but has seen the 
disease caused by dermatocoptes cuniculi in rabbits, and Zurn states 
that dermatophagus cuniculi produces the same result. Cadiot ascribes 
parasitic otitis in the dog and cat to the presence of Symbiotes auricu- 
arum and in the goat and rabbit to Psoroptes communis. Ostertag 
bund bird-lice (Gamasus auris) in the external meatus of a cow: 
attention was drawn to the animal by its violently shaking its head In 
dogs facial eczema sometimes invades the external ear, and, on the other 
hand, otorrhoea may produce eczema on the ear. 
Two kinds of otitis externa are distinguished—the acute and chronic. 
le acute develops m the dog as a sequel to eczema of neighbouring 
parts or following the entrance into the meatus of discharges from 
neig lbourmg wounds. A yellowish-brown secretion, usually mixed with 
pus flows from the ear, and produces eczema of the skin below. Proper 
treatment often induces recovery in eight to fourteen days. 
In neglected cases chronic otitis develops. It may be divided into a 
supei facial and deep form. The first is commonest in dogs, and owes its 
ongm to irritation produced by decomposing secretions. Abnormal 
piuritus is present; the unpigmented skin of the meatus is reddened 
and coveied with a blaclash-brown fatty material; light pressure at the 
