CONFERENCE ON TUESDAY, JULY 3, 1883, 



The MARQUIS OF HAMILTON in the Chair. 



FISH DISEASES. 



THE title of the present paper is, I am sorry to say, far too 

 large for its contents, for I propose to speak, not of fish 

 diseases, in general, but of that particular malady which 

 attacks freshwater fishes, occasionally assumes the dimen- 

 sions of a very formidable epidemic, and, in one of its 

 forms, the so-called " Salmon disease," is too well known. 



At the first onset of this disease, small whitish patches 

 make their appearance on the skin of the fish. The 

 smooth integument of the top of the head, or of the end of 

 the snout, is a very usual locality, but the adipose fin, and 

 the axillae of the paired fins are also among the first parts 

 to be affected. If there is an abraded or wounded 

 surface, the disease is pretty sure to attack it, but the 

 invasion of the malady is in nowise dependent upon the 

 pre-existence of an injury. In severe cases, the mischief 

 rapidly extends, until sometimes almost the whole body is 

 covered with an ashen grey coat, which completely hides 

 the scales. On brushing off the crust, however, the scales 

 are usually found undisturbed. In the scaleless parts of 

 the skin, sloughing soon sets in, and deep burrowing sores 

 are formed. On the head, the cranial bones may be 



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