have found it exhibits itself in a very peculiar but very definite way. 

 It occurs mainly among two to three inch brook trout fingerlings. 

 The first manifestation is the development of gray spots in the region 

 or directly over the cerebral hemispheres, the spots increasing in size 

 and finally running together. About this time the fish begins to 

 gyrate in a more or less spiral fashion, which movements always, as 

 far as observed, end in death. At the hatchery we have termed this 

 disease the "whirling sickness" or the "cerebral spot disease." In 

 every instance the organism in great numbers has been isolated from 

 the local lesions and the heart's blood. This organism has been shown 

 by Marsh to be of a pleomorphic type, that is, it exhibits different 

 forms under different conditions. The writer believes that a number 

 of diseases may be caused by different strains of this organism in 

 somewhat the same sense that we have different strains of the Pneu- 

 mococci and typhoid bacilli. Dr. David L. Belding, of Massachu- 

 setts, has been confronted with what appears to be the same organism, 

 producing in the adult brook trout ulcers which usually prove fatal. 

 We have begun a comparison of these organisms with the belief that 

 there is close relationship between the two. 



In making attempts to combat this disease, after learning the 

 morphological and cultural characteristics of the organism, the plan 

 was to ascertain the source and mode of infection. Attention was 

 then directed to the water supply and the food. The food used at 

 the Hackettstown hatchery consists of butterfish, beef liver, pork 

 melts, and sheep plucks. Samples from different lots of this food 

 taken from cold storage were examined, and organisms not unlike 

 those above described were isolated from the sheep hearts and the 

 beef livers. It was not possible to carry out the work sufficiently to 

 prove that the organisms were normal to the beef and sheep, as these 

 animals are warm blooded, while fish are cold blooded. It is quite 

 possible for an organism of this type to gain access to the food men- 

 tioned on being handled. 



The lactic acid bacillus is not present in milk while in the udder 

 nor is it introduced into the milk intentionally, but always gains 

 access on subsequent handling. If the food is proved to be a carrier 

 of the organism, sterilization would eliminate it. If the water is the 

 agent of transmission, the destruction of the bacteria would be a dif- 

 ficult problem in view of the fact that any germicide now recognized 

 for the treatment of water would have a very harmful effect on the 

 fish. On the other hand, the organisms isolated from the heart's 

 blood and from the local lesions in the fish have proved to be very 

 resistant to germicidal agents. In laboratory experiments these bac- 



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