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Proceedings of the Royal Society 
scaled parts of the body. The minnow had only one patch of 
fungus upon it, which was seated within its mouth on the inner 
margin of the right lower jaw; it filled the mouth, which was 
distended by its growth ; and every other part of its body was free 
from fungus or blemish of any kind. 
The reason why most of the fish affected with fungus are first 
attacked by it upon their heads may arise from various causes. All 
river fish present their heads to the downward current of the water 
whether they are swimming or at rest, and as the spores of the 
fungus are floating down with the stream, the heads of the fish are 
the first parts to come in contact with and be affected by them. 
Further, the mucous glands are most numerous and active upon the 
head of the fish, which is also more thickly covered with mucus 
than other parts of the body, and the spores which fall upon it 
adhere more readily ; and the fins and tail, from their continuous 
waving motion, are more liable to arrest the passing spores than the 
parts of the body from which they spring, and, from this cause, 
are generally affected sooner than the bodies of the fish. 
The numbers of the dead and dying fish of all kinds removed from 
the river Eden in 1878 by the police, and published by Mr Buck- 
land in his report for that year, show that there were 1271 salmon, 
140 fresh- water trout, and 40 brandlings or parr, being over 50 of the 
large fish to every one of the smaller. About 1000 of the salmon 
were clean fish, and it may be inferred that the trout and parr were 
also clean, which goes far to show that the so-called disease is as 
much a mechanical as a functional one. Further, from documents 
descriptive of the effects of the disease in the river Tweed, in the 
lower district, during this season 1879, which were collected by the 
police from taxmen and practical fishermen on the river, I find that 
the proportion of large fish affected, dead or dying — namely, salmon 
and sea-trout — is very great compared with the smaller fish, 
which were found to be affected in a similar way. The smaller 
fish alluded to consist of river-trout, greyling, smolts, perch, and 
grey mullet. 
From observation of the fungus and of the fish affected by it, I 
am led to believe that the so-called salmon disease does not depend 
upon a pre-diseased condition of the fish. It is a true parasitic 
attack to which every fish in any affected river seems to be liable, 
