372 



Patt III — Seventh Annual Report 



inilictod. With regard to this, Mr Stirling quoted the following passage 

 from a letter written to the Field, on 25th May 1878, by Commander 

 Duncan Stewart, K.N.: — 'In regard to the disease from which salmon 

 ' are suffering in some of our rivers, it may be of advantage that I should 

 1 mention what I observed in a small river at the head of Castrie's Bay in 

 1 Siberia. I found the river rather low, but with plenty of clear running 

 ' water. But what astonished me was to see thousands of salmon in all 

 ' stages of disease and death, some darting away, but soon stopping to rub 

 ' the side on the bottom or on a rock ; others were constantly rubbing, 

 ' others unable to rub. In those last cases large sores, from the size of a 

 'shilling to that of a half-.-rown, of a most filthy appearance, were always 

 ' present. Fish on which scales had been rubbed off would try to get 

 ' out of my way, but I could kill them with a stick ; those with the skin 

 1 gone would rub themselves against my trousers.' After a fish has been 

 for some time affected, and the disease progressed so as to form large 

 patches upon it, the irritability seems to disappear in great measure. 

 This sluggishness so distinctly manifested by such a fish cannot always 

 be held as due to its being in a dying condition, as in many cases one 

 finds it possessed even then of considerable muscular power, as may be 

 well seen if an attempt is made to drag it out of the water, and further, I 

 have had ample evidence of this from having had affected fish under my 

 observation, when I have noticed such a manifestation of sluggishness 

 thirty-six hours before death. 



One of the bailiffs on the South Esk informs me that he has observed 

 that fresh fish coming up from the sea if they get slightly affected by the 

 disease, much sooner become sluggish or 'sick' than those fish which 

 have been long in the river do, although the latter may be much diseased. 



So far, we have not been able to observe any distinctly pathological 

 appearances in the viscera, with the sole exception of evident congestion 

 of the spleen, which, however, did not show any marked evidence of 

 enlargement. However, the number of specimens examined preclude the 

 assertion that even this condition is always present. On subjecting a 

 portion of the furry fungus-covering to close examination, it is seen to 

 present a peculiar appearance aptly designated by Professor Huxley as 

 ' wet-paper ' like. This appearance, however, is only manifested when it 

 is examined out of the water. If a fish dead of the disease be left in 

 water for a little time the filaments of the ' wet paper ' like mass unfold 

 themselves partially and then it is seen to have a greyish woolly appearance. 



If a portion of the mass be removed and placed under the microscope, 

 it is seen to be composed of very long tubes having very thin and 

 delicate walls, consisting for the most part of cellulose. 



The diameter of the tubes varies greatly, but the average may be 

 stated as 10/x (If- = -25^170" °f an i ncn ) Dut they may be so narrow as 

 only to have a diameter of S/xor even less, while others are found in which 

 the diameter may be 40/x. 



The tubes are lined by a layer of fine colourless protoplasm, and within 

 this there is usually included a variable amount of granular protoplasm 

 irregularly disposed among a large mass of fluid. The granules of proto- 

 plasm are themselves irregular in form, and many vary in size from up 

 to that of masses 6/x in diameter. In some cases the filaments seem abso- 

 lutely empty, and when so are difficult to define being absolutely colourless. 

 The filaments are, for the most part, unbranched, but at wide intervals 

 lateral branches are given off. 



If a filament be traced upward it may be found to taper slightly to its 

 termination, containing here no granular protoplasm and ending blindly in 

 a rounded and tapering extremity. This is usually the rule during the 



