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Part III. — Seventh Annual Report 



there always occurs a few cases of fungussy fish after an east wind has 

 been blowing, more especially if the fish have been previously fed. 

 Such fish always are somewhat dry to the touch after the exposure of 

 the pond to the wind, and show signs of gastro-intestinal disturbance. 

 That the wind has something to do with this has been proved by putting 

 up a screen at the side of certain ponds and leaving others unscreened, 

 when fish only became fungussy in those unprotected by screen. 



In other cases there seems to be pretty evident signs that certain sexual 

 conditions of ill health predispose to the fungus growing. From such con- 

 siderations, it seems possible to infer that the fungus is a secondary con- 

 dition, only attacking fish which are out of health; but while this may be 

 applicable to the sporadic eases, it is scarcely credible that it can apply 

 to the epidemic cases. The point which calls for investigation is, I think, 

 this. Is the fungus which is thus found in sporadic cases identical with 

 that which is found in epidemics among river salmon? The theory of 

 overstocking of fish has been advanced as the principal cause favouring 

 the onset of the disease, and this is probably an efficient factor in determin- 

 ing an epidemic. We are well aware of the fact that when certain 

 diseases of an infectious type, such as typhus fever, affect a large city, 

 it is most deadly and spreads most rapidly in those parts where there 

 is overcrowding of the inhabitants. 



Mr Stirling cited as an argument against overcrowding, the following 

 experiment conducted by the Tweed Commissioners in 1874. They 

 'constructed a small pond for experimental purposes, which measured 

 '36 feet, by 16 feet, on the side of a small stream called 

 1 Oarham Burn, from which a run of water was supplied to the 

 4 pond by a drain pipe. On 7th May 1874, 130 sea-trout smolts, 

 1 the average length of each being 8 inches, were taken from the Tweed 

 ' and placed in this pond. After an interval of two years they were 

 ■ specially examined, weighed, and measured on the 25th May 1876. 

 1 Seventy fish were found in the, pond, the average length of each was l'2h 

 ' inches, they were now in the whitling stage, and in fine condition. 

 1 After another interval of two years, there was another examination . . . 

 ' when sixty-six sea-trout of the average length of 14§ inches were found 

 ' in the pond. They were kept here free from fungus for a further 

 ' period, making in all five years, during which time they were kept 

 ' cribbed, cabined, and confined, in a pond no larger than an ordinary 

 ' dining-room, and remained in health during that period without 

 ' exhibiting any sign of fungus disease, and this although the pond 

 ' is situated within a few hundred yards of the Tweed — an affected 

 4 river.' This experiment proves certainly that in a crowded pond the 

 disease cannot occur spontaneously, and is thus an argument, if that is 

 needed, against 'spontaneous generation,' but nothing farther. This 

 experiment might with considerable advantage to our knowledge, have been 

 carried further by their putting into the pond a fish of the same kind, 

 but already affected with the disease. In this way it would have been 

 well determined whether or not overcrowding is the principal factor in 

 determining the spread of the disease, from a sporadic case, in an epidemic 

 form. The disease, however, may attack fish although there is no j re- 

 disposing cause in the form of overcrowding, and an instance of that has 

 lately come under my own observation. We have had a fine specimen of 

 a char living in a tank alone, and supplied with 200 gallons of water since 

 the 25th February. On Monday, the 1 1th March, a few patches of fungus 

 were noticed on the snout, and it died two days later. On examination 

 after death, I found the snout covered with the fungus, which extended 

 up to the eyes, and leaving them untouched, passed for an inch beyond 



