[3] OPERATIONS AT m'CLOUD RIVER STATION. 739 



five minutes after there was no sign of breathing and no feeling, and 

 still found the heart beating. The fish are all fat and nice to look at, 

 and I can find no trouble with eyes or gills or any other part, except 

 the stomach seems a little hard and drawn up, and a hard and con- 

 tracted yellow substance sometimes appears around the heart and 

 stomach. 



The disease has been very severe in the McCloud River, and I feel 

 sure that it was introduced iuto the ponds by transferring fish to them 

 from the river. It seems to be a clearly contagious disease, as in one 

 pond, which received no fish from the river and where the water flows 

 directly to the pond from the flume without running over any other fish, 

 no trout have been affected. 



The water in the river this autumn has been much lower thau I have 

 ever known before, and has been of a milky, muddy color all summer, 

 owing to the overflow from Ash Creek. The very hot weather melts 

 the snow on Mount Shasta, which has been reduced much more than 

 usual this summer and fall, some of which empties through this creek, 

 and when very high the creek overflows its banks and carries quantities 

 of ashes into the McCloud Eiver. 



The large trout suffered from this disease much more than the small 

 ones. It was thought that the changed weather and heavy rains late 

 in the fall would stop the progress of the disease, but it did not seem 

 to do so. The temperature of the water while the fish were dying was 

 about 58 or GO degrees Fahrenheit. 



Some specimens of these diseased trout were sent to Prof. S. A. Forbes, 

 of Champaign, 111., with the result of his making a careful examination 

 and reporting as follows : 



In these six specimens the kidneys were evidently the principal seat 

 of disorder, the spleen being also considerably affected, and the liver 

 much less so* The muscular tissue of the heart was involved in the 

 single specimen that I examined in that particular. 



The kidneys were as black as coal and as soft as mush, a condition 

 explained by microscopic sections, which show the urinary tubules 

 little altered, with their epithelial lining intact, but all the other tissues 

 (the connective tissue, capillaries, &c.) almost wholly replaced by a 

 mere pulp of pigmented corpuscles, black pigment granules, and mi- 

 crococci, in which lie imbedded vast numbers of spherical corpuscles 

 each containing an embryo parasite. These encysted parasites are so 

 numerous that the kidney pulp is seen to be everywhere thickly 

 speckled with them. 



The spleen is much pigmented, like the kidneys, but less so, and 

 the liver still less than the spleen, the pigment cells being much the 

 most abundant about the blood-vessels, and often blocking the cap- 

 illaries, especially in the liver, and causing the degeneration of large 

 tracts of the gland substance. A similar disorganization of the liver 

 cells frequently appears at a distance from arteries or veins. The 



