72 



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Reactions of 

 Fishes to Habit-forming Drugs 



The reactions of goldfish to certain 

 habit-forming drugs is the subject of an 

 article in the Journal of the American 

 Pharmaceutical Association, by Prof, 

 Victor E. Shelford, of the University of 

 Illinois. The craving engendered by the 

 use of habit- forming drugs is not under- 

 stood. Most of the pharmacologic stud- 

 ies in this connection have been made on 

 mammals (a few have been on frogs), 

 but almost none on the lower vertebrates. 

 By chance Professor Shelford discovered 

 that fishes are peculiarly affected by nu- 

 merous organic substances in aqueous 

 solution when put under special experi- 

 mental conditions. The conditions are 

 established in a tank approximately 48 

 inches long, 5 inches deep and 6 inches 

 wide, in which water containing a drug 

 flows into one end and out at both top 

 and bottom, at the middle, while water 

 which contains none of the drug flows 

 into the other end at the same rate. The 

 two flows meet at the middle and with 

 most substances there is a mixture of the 

 two kinds of water which occupies the 

 centre third of the tank. In this mixture 

 a fish moving from the pure water end 

 toward the drug-containing end encoun- 

 ters a gradual rise in concentration of the 

 drug. This region of change of concen- 

 tration is called the gradient. The char- 

 acter of the gradient in these tanks has 

 been fully determined by taking samples, 

 by measuring and by the use of colored 

 water. If a fish encounters no change 

 in water, it moves freely back and forth 

 without showing preference for either 

 end of the tank. If it encounters water 

 containing an excess of carbon dioxide, 

 it backs away and starts again, often re- 

 peating the operation before going for- 

 ward. It gives other evidence of stimu- 



lation. The opercles are lifted, the lower 

 jaw protruded, or the mouth moved in a 

 yawning, coughing or gulping motion. 

 When a fish enters a solution containing 

 ethyl-alcohol, cocaine, morphine or any 

 one of several other substances tried, 

 there is no apparent rejection of the drug, 

 but, on the contrary, after a time the fish 

 is found to have a preference for the 

 drug-containing end of the tank. With 

 cocaine the fishes, after a short exposure, 

 refused to leave the drug solution, soon 

 became intoxicated and died. With 

 ethyl-alcohol the fishes reacted more and 

 more positively as the concentration in- 

 creased up to 10 per cent. The experi- 

 ment was discontinued because the sub- 

 jects became semi-intoxicated. In 20 per 

 cent, ethyl-alcohol the fishes avoided the 

 full strength, but still reacted positively. 

 With morphine no preference is shown 

 in concentrations of 0.15 g. per litre. In 

 1 g. per litre positive preference was 

 shown by one individual, but not by an- 

 other. Some individuals avoided the 

 strongest solutions of morphine. With 

 naphthalene in half : saturated and sat- 

 urated solutions, the fishes reacted pos- 

 tively, although they died after a time. 

 Some species of minnows were less sensi- 

 tive to ethyl-alcohol than goldfish. 



The goldfish is becoming a great pest. 

 It has multiplied in the River Murray 

 to such an extent that a frayed rope-end 

 let down into the water will in a few days 

 be a mass of goldfish spawn. These wild 

 goldfish grow up to two or three pounds 

 in weight, many of the largest being red. 

 —Herbert M. Hale, Australia. 



We recently heard of a house that 

 found a tenant solely because it happened 

 to have a glass-enclosed sleeping porch. 

 To aquarists, nuf sed ; to property own- 

 ers, a hint of a desirable improvement. 



