attracted few workers although so much of 

 selective toxicity is actually applied comparative 

 biochemistry." 



The program of screening compounds for 

 use in a carp bait encountered the usual diffi- 

 culties. None of the 1,496 chemicals reported 

 on here proved suitable for incorporation into 

 a bait (on a solubility -palatibility basis), but 

 the force -feeding tests do provide the only ex- 

 tensive acute oral toxicity data on fish available 

 today. Accordingly the authors hope that others 

 will find this material useful as a reference for 

 future studies. 



DEVELOPMENT OF EXPERIMENTAL 

 MATERL\LS AND TECHNIQUES 



A laboratory was constructed and simple 

 techniques for capturing and holding carp, ob- 

 taining chemicals, force -feeding, and tagging 

 were devised before force-feeding could be under- 

 taken. 



The Fish Laboratory is located below a 

 clear, continuously flowing, constant-temperature 

 (47° F) spring with a capacity of 50 to 100 gallons 

 of water per minute . The water , of pH 6 . 7 , 

 contains 10 p. p.m. of alkalinity and traces of 

 other compounds and elements. It is fed into 

 large tanks by gravity through nontoxic, black - 

 iron pipes . 



The carp were held and observed in 13 

 glass -fronted, fiberglass tanks (Loeb, 1959) of 

 350 and 550 gallons capacity. Each tank is in- 

 dependently maintained at any desired temperature 

 by stainless -steel or aluminum coils connected 

 to a closed-circuit oil -burning system and con- 

 trolled by a solenoid and thermostat. The tanks 

 are nontoxic to fish and other forms of life and 

 require no maintenance. 



The test carp were captured with an 

 alternating-current electric boat shocker in the 

 New York State Barge Canal. After transporta- 

 tion to the laboratory by tank truck supplied with 

 oxygen, they were held for weeics at spring tem- 

 perature of 47°F. The fish ranged from 1 to 10 

 pounds in weight but averaged around 3 pounds. 

 Poor-quality fish were rejected. 



The compounds force -fed to the fish were 

 solicited from governmental, educational, and 

 private agencies (table 3). Since it was im- 

 possible to accurately predict the effect of in- 

 dividual chemicals on carp, the majority of 

 compounds were picked by the agencies in random 

 fashion, and a great variety was received. All 

 of the compounds reported on were accompanied 

 by chemical names, many of which were changed 

 to conform to the Chemical Abstracts system. 

 A number also have trivial or trade names, listed 

 in table 2. 



Development of a method of force -feeding 

 proved to be difficult, but the final technique 

 (Loeb and Kelly, 1960) was completely adequate. 

 For many fish, force-feeding is relatively simple 

 because direct access to the stomach may be had 

 through the pharynx. Carp, however, possess 

 pharyngeal teeth which form an effective barrier 

 to an ordinary probe. Accordingly a machined 

 aluminum tube was developed in a shape which 

 allowed it to be forced past the grinding mill 

 formed by the pharyngeal teeth and the basi- 

 occipital bone and into the thin -walled esophagus 

 where the capsules containing the poison were 

 deposited. A fiber glass rod was used as a 

 plunger . The technique is an art but properly 

 performed is almost always successful. 



During the force-feeding operation the 

 carp were immobilized in a nose -up position by 

 a specially constructed device employing foam- 

 rubber jaws and activated by compressed air 

 (Kelly, 1959). 



The force -fed fed fish were marked on 

 the jaw or fins with brightly colored, paper 

 laundry tags (Kelly and Loeb, 1959) or with 

 colored thread tied to the serrated dorsal and 

 anal spines. 



The chemicals to be tested were placed 

 in one or two No. 5 gelatin capsules by means 

 of an eyedropper or drawn glass funnel. 



SCREENING PROCEDURE 



The basic objective of the force -feeding 

 program was to discover compounds that were 

 lethal at low doses of 30 milligrams or less of 



