456 BULLETIN OP The bureau of fisheries. 



Of 30 wild trout injected in the thyroid region with 2 minims each of tumor 

 ground with an equal volume of salt solution, about half died from the immediate toxic 

 effect of the injection. At another trial one-tenth cubic centimeter of material made 

 from several tumors was injected into each of 15 domesticated trout. Eleven of them 

 succumbed almost immediately. The material was then diluted until it contained 3 

 volumes of salt solution and 15 more fish were injected, but 12 of these died within 2 or 

 3 hours. Seven fish were injected subcutaneously near the dorsal fin with one-fifth 

 cubic centimeter of this material, and 5 died within a short time. One cubic centimeter 

 was, however, passed into the stomach of i trout, and one-half cubic centimeter each 

 into the stomachs of 3 others without apparent efifect. This particular sample of com- 

 bined tumor substance was unusually toxic. 



The trout dying from the immediate physiological effect of trout tumor substance 

 ground with salt solution showed a fairly characteristic picture of symptoms, ending in 

 tetany. The mechanical effect is little, as shown by the control fish. In the few 

 cases where the shock from trauma is apparent the fish lies on its back or side, scarcely 

 breathing, and recovers in a few seconds. The inoculated fish, however, were evidently 

 poisoned. They became immediately distressed, swam in circles or in short, frantic, 

 and aimless dashes about the trough, then fell greatly weakened upon their sides and 

 lay there with short and rapid breathing until the next paroxysm. Finally they suc- 

 cumbed in tetany, some with gills widely distended and marked opisthotonos. Even 

 the survivors seemed to be much weakened. 



Forty-three wild brook trout were inoculated in the thyroid region with small 

 portions of tumor taken directly from the fish without grinding or mixing with salt 

 solution. Pieces were forced through the floor of the mouth by means of trochar, probe, or 

 seeker. The material was more or less toxic even in this form, and the mechanical injury 

 and bleeding were greater than with the needle, but 24 of the 43 trout survived. 



Ten domesticated brook trout were injected in the thyroid region with one-fifth of a 

 cubic centimeter each of a mixture of one volume of domesticated brook trout blood 

 and three volumes of physiological solution. No loss attended the operation, and the 

 fish have never shown any but the immediate reaction to the inoculation. 



In all injections and inoculations the instruments used were sterile, and the tumor 

 material obtained as free from contamination as possible. It is not usually possible to 

 obtain in quantity the thyroid tumor material from fish in a completely aseptic condition. 



Mud from one of the fish ponds (no. 10) constantly associated with tumor fish was 

 injected into the stomachs of 25 domesticated trout and of 20 wild trout. The dose 

 was repeated on the former lot after three days. The filtrate of this mud through paper 

 was injected into the thyroid region of 25 domesticated trout and behind the eyeball 

 of 17 domesticated trout. The dose was 2 to 2^ minims. These fish have shown no 

 results from the inoculations. 



Trout tumor material has been ground with sand and filtered through a Berkfeld 

 filter. The filtrate has been injected into the thyroid region of 2-year-old domesticated 

 trout, all manipulations being carried on in the cold. About 0.3 to 0.4 cubic centimeter 

 of filtrate was given each of 9 trout. These were kept under observation for over four 



