312 SPENCER WALPOLE AND T. H. HUXLEY. 



many rivers. The disease was noticed originally in the 

 autumn and spring of 187T in two rivers, the Esk and the 

 Nith, which flow into the Solvvay Firth. It soon spread to 

 the Eden and other adjoining rivers. In the spring of 1879 

 it was observed in the Tweed, when it rapidly became very 

 serious, and in 1880, when a commission was appointed to 

 investigate it, it had extended to the Nith, the Annan, the 

 Esk, the Eden, the Cree, and the Dee, all flowing into the 

 Solway Firth ; to the Doon and the Ayr in Ayrshire ; to the 

 Derwent in Cumberland, the Lune in Lancashire, and to the 

 Tweed. Since then the disease has broken out in the Seiont, 

 the Ogwen, and the Conway in North Wales, and in the 

 Tay and North Esk in Scotland. 



We have very little doubt that the disease which first 

 excited attention in 1877 had existed, at any rate in a 

 sporadic form, for many years. It was stated in evidence 

 before the late commission that Dr. Crosbie, formerly sur- 

 geon to the " Challenger" expedition, carefully investigated 

 a case of the disease so long ago as in 1852. His observa- 

 tions will be found in the Commissioners' Report, p. 44. 

 Other witnesses similarly stated to the commissioners that 

 they had observed sporadic cases of the disease for years. 

 We may add that we have recently understood from a lessee 

 of fisheries on the North Esk that he had seen diseased fish, 

 without recognising them as diseased, for very many years ; 

 and we have very little doubt that sporadic cases of the 

 disease occur in almost every river. 



The first symptom of this disease is the appearance of 

 small greyish or ashy discolorations of the skin, usually 

 upon those parts of the body which are devoid of scales, 

 such as the top and sides of the head, the delicate valvular 

 membrane on the inside of the jaws, the adipose fin, and the 

 soft skin at the bases of the other fins. Where such dis- 

 coloured patches occur on the scaly parts of the body the 

 scales are hidden by a film, and it might readily be supposed 

 that they had been detached. But if the discoloured film is 

 gently washed or wiped ofl*, the scales will be found beneath 

 perfectly undisturbed. On the scaleless part of the body, 

 also, the discoloured places often look as if they were the 

 eff"ect of bruises or abrasions, but careful examination of the 

 skin fails to reveal any evidence of external injury. 



The exact character of this aff'ection of the skin may best 

 be observed in the recently formed isolated patches, not 

 bigger than a sixpence, in which the disease appears on the 

 soft integument of the head. Such a patch is usually nearly 

 circular and has a well-defined margin separating it from 



