ITS CAUSES AND SYMPTOMS. 
151 
of tlie thyroid varies considerably in certain animals, especially in horses. 
Not infrequently its lobes, normally the size of a chestnut in the horse 
and ox, become as large as a duck’s egg, whilst the commissure remains 
little affected. This liability to variation is widely observed in particular 
families, and appears, to a certain degree, to be inherited. Such con¬ 
ditions cannot consistently be described as goitre, for the gland, although 
abnormal, does not continue to grow larger. Many references to inherit? 
ance and enzootic outbreaks of goitre in animals qre clearly to be referred 
to this condition. 
Symptoms. The most striking feature is the swelling close under the 
larynx, and towards the side of the trachea. In horses the gland op 
either side, usually not larger than a chestnut, attains the dimensions 
of a man’s fist. It sometimes becomes as large in dogs. As the gland 
grows in size and weight it sinks, and becomes more prominent. Either 
one or both sides may be affected. In dogs it is easily displaced, and 
may descend as far as the lower portion of the neck, and lie immediately 
in front of the chest; but it seldom exhibits inflammation, pain, or 
increased temperature. 
As long as the size of the thyroid is not much increased, goitre in 
animals is of little significance. In the horse, however, Massot and 
Truelsen have observed dyspnoea from the swelling pressing on the trachea, 
This occurs more often in dogs, which may be unable to lie down, on 
account of the swelling compressing the trachea and interfeiing with 
breathing. The animals live for some time continuously suppoited 
on the extended front legs, until finally it becomes necessary to kill 
them. The trachea may be narrowed until it closely resembles a scab¬ 
bard. Zscliokke found carcinomata in dogs invading the trachea and 
oesophagus, and producing difficulty both in breathing and swallowing. 
Johne reports the case of a dromedary calf which died at birth from 
suffocation produced by a goitre swelling weighing nearly IB pounds. In 
a horse, sarcoma of the thyroid spread entirely over the laiynx duiing 
the space of a year and a half, and finally caused death by suffocation. 
Prognosis. In animals, and especially in young dogs, goitre is not 
simply a blemish, although some varieties occurring in horses cause no 
inconvenience. The significance of the case depends upon the size of the 
swelling and its rate of increase, but our knowledge of the condition does 
not justify very sanguine expectations. Extirpation entails not only 
the danger of excessive bleeding, but also the development of peculiar 
symptoms described as cachexia strumipriva, which are frequently seen 
in young dogs. Some weeks after removal of the thyioid in its entirety, 
marked weakness appears, accompanied by anaunia and v a sting, fioin 
which the animals finally die. These symptoms, however, can be 
prevented by giving a daily dose of fresh thyroid gland, Goitie, in man, 
