1882.] On the Epidemic known as the " Salmon Disease." 381 



Venn, John, M.A. T 

 Walker, John James, M.A. 

 Warrington, Robert, F.C.S. V 

 Watson, Professor Morrison, M.D. 

 Weldon, Walter, F.C.S, F.R.S.E. 



The following Papers were read : — 



Williams, Charles Theodore, M.A., 



M.D., F.R.C.P. 

 Wright, Professor Edward Per- 

 ceval, M.A., M.D., F.L.S. 



I. "A Contribution to the Pathology of the Epidemic known 

 as the ' Salmon Disease.' " By Professor T. H. Huxley, 

 LL.D., F.R.S. Received February 21, 1882. 



For some years, an epidemic disease, followed by a very large 

 number of deaths, has been observed to prevail among the salmon of 

 certain Scottish and British rivers, from the Tay,* on the north, as far 

 as the Conway on the south. 



The first obvious symptom of the malady is the appearance of one 

 or more greyish patches upon the skin of parts of the body which 

 are not covered with scales, such as the top and sides of the head, the 

 adipose fin, and the soft skin at the bases of the other fins. 



Such a patch, when it first attracts attention, may be as big as a 

 sixpence. It is nearly circular, with a well defined margin and a some- 

 what raised softer centre, from which faint ridges radiate towards the 

 circumference. It is important to observe that a single small patch 

 of this kind may be seen on the skin of a fish which, in all other 

 respects, is perfectly healthy, and when there is no indication that the 

 skin has ever been bruised or abraded in the place occupied by the 

 patch. The patch, once formed, rapidly increases in size and becomes 

 confluent with any other patches which may have appeared in its 

 neighbourhood. The marginal area, as it extends over the adjacent 

 healthy skin, retains its characters ; but the central part undergoes an 

 important change. It takes on the consistency of wet paper, and can 

 be lifted up in soft flakes, as if it were a slough, from the surface of 

 the derma or true skin, which it covers. In fact, it is obvious that 

 this papyraceous substance has taken the place of the epidermis, so 

 that the sensitive and vascular true skin is deprived of its natural 

 protection. As the patch spreads, the true skin beneath the central 

 papyraceous slough ulcerates and an open bleeding sore is formed, 

 which may extend down to the bone, while it passes outwards into 

 burrowing sinuses. 



When the disease has reached this stage it obviously causes great 

 irritation. The fish dash about and rub themselves against stones, 

 and thus, in all probability, aggravate the evils under which they suffer. 



* Within the last few days I have received specimens of diseased fish from the 

 North Esk. (March 8.) 



2 f 2 



