230 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 



fragments in the fresh state, fibers are seen, which, in places, have pre- 

 served their normal aspect and their striation, and at other points more 

 or less considerable spaces, where the muscular substance is filled with 

 a vitreous refringent mass, around and in the intervals of which lie 

 fatty droplets, yellowish granules, and spores. The degeneration invades 

 gradually the muscular substance of the primitive fibers, and one finds 

 it in parts of these elements, where the parasite appears not to have 

 penetrated. On the contrary, the neighboring, noninfested, primitive 

 fibers seem exempt from that alteration, and one frequently observes a 

 degenerated fiber surrounded by healthy ones. 



The fiber thus degenerated and broken up, is soon invaded by pha- 

 gocytal cells coming, some from the sarcolemma, others from the con- 

 nective tissue. This latter, at the diseased points, is the seat of a very 

 marked irritative proliferation. 



It is necessary to distinguish, in the degenerated fiber, the parts 

 where spores are found in great number, and those where these elements 

 are few or absent, the degenerative process in the latter case having 

 originated from the presence of the parasite at a difterent point. 



In this latter case the cells which have penetrated into the degen- 

 erated tissue multiply rapidly; in proportion as their number augments, 

 one sees the muscular debris diminish ; very soon they have completely 

 disappeared, the place of the fiber being finally occupied by connective 

 tissue. While these phenomena occur, the irritation is propagated, the 

 connective-tissue proliferation extends itself, and a sclerosis of the 

 neighboring muscle region, with atrophy of the primitive fibers, is pro- 

 duced. 



At the points where the degenerated fiber incloses a great number 

 of spores, the formation of connective tissue is at first limited to a 

 thickening of the perimysium. There are thus formed connective-tissue 

 bridges, separating the spaces occupied by the spores, and which 

 correspond to disappeared primitive fibers. Tliese facts are seen 

 especially clearly on transverse sections. Little by little these bridges 

 increase in thickness, at the same time their tissue becomes more dense; 

 they thus form around each space a fibrous shell, which tends to con- 

 tract more and more. There seems to be here a true encystment of 

 the parasite, such as is produced around foreign bodies introduced into 

 the tissues. 



Symptoms. — Barbels attacked are less lively than usual and have 

 much difQculty in ascending streams; surface of body, dull, grayish 

 yellow, oily, slippery (Meuse; Kailliet). 



Less lively than usual, easily caught in the hand, breasting the cur- 

 rent with difficulty, avoiding rapid water (their usual haunt), taken in 

 great numbers in bow-nets. Some affirm, others deny, that the sick 

 fish will not bite at the hook. Diseased fish are of all sizes. Those 

 seriously affected are of a weight much below that indicated by their 

 external appearance, the body being in fact more or less dilated. On 



