MELANOSIS. 
377 
tain observed phenomena when the animal was living. First, the 
difficulty which occurred in mastication, and holding of the head 
to the right side. Secondly, the atrophied and palsied state of the 
muscles of the left side of the head and face ; and, thirdly, the 
turgidity of the veins of the same side. If we consider the func- 
tions of the facial nerve, the vagus, the glosso-pharyngeus, and 
the recurrent laryngeal, we shall at once perceive, that, if their 
force or influence be cut off* from the organs or parts to which they 
are distributed, derangement in the functions of those parts will 
at once ensue : hence the reason of the disturbance in the res- 
piration and the loss of motor power in the muscles of the deft 
side of the head and face, and, as a sequence to this loss of motor 
power, the atrophy or waste of the muscles themselves. The tur- 
gidity of the veins is also accounted for, from the fact of the max- 
illary vein being pressed upon so as to prevent the blood flowing 
towards the heart. A great number of the small superficial veins 
of the head empty their contents into the maxillary vein ; conse- 
quently, any thing impeding the flow of blood through the latter 
would also impede its flow through the former. 
In 1813 an individual in France, named Gohier, published some 
observations upon this disease; and he advanced the opinion “ that 
melanosis probably depends on the increase or diminution of some 
of the elements which enter into the composition of the body of the 
white and grey horse, or in some remarkable change in the nature 
of the secreted fluids. “ The carbon which is found in melanosis is 
too easily separated by calcination to permit us to ascribe the 
colour of this disease to any other substance*.” Professor Dick, 
I believe, holds a somewhat similar opinion ; he maintains that the 
dark pigment which should be distributed generally through the 
hair is removed after its formation, and deposited locally, and that 
thus the dark matter formed in this disease is accounted for ; and 
if I remember aright, he stated, in one of his lectures he published 
in “ The Lancet” many years ago, a paper wherein he had sug- 
gested the above opinion. For my part, I do not see any thing 
absurd in the supposition that melanosis essentially arises from the 
black or dark matter of the hair being deposited in one or more 
localities, instead of being distributed over the hair covering the 
entire body. I am not aware that any cases are recorded of the 
disease occurring in young horses; neither am I sure that it has 
ever been noticed to occur so long as the hair generally retained its 
original shade of colour. In every case I hear or read of, the 
animal, before or at the time the disease became manifest, was 
or had been noticed to have become lighter in colour; and if 
Cyclopaedia of Practical Medicine, vol. iii. 
