Biological Survey — Erie-Niagara Watershed 141 



the purpose of the original work, namely, the improvement of 

 streams and the quality of fish used for stocking. 



Blood from natural fish can only be obtained in the field in 

 cooperation with an effective collecting unit that is used to hand- 

 ling live specimens. Transfer to the field laboratory must be care- 

 fully made. In the portion of the paper devoted to the experi- 

 mental work the effects upon the blood of some of the common 

 accidents will be shown. 



Experiments Upon Fish Blood. — Three methods are described 

 in most German texts for obtaining samples of blood from fish, 

 slipping the gill, cutting the end of the tail and bleeding from 

 the heart. We have tried all methods and find only the last satis- 

 factory, if one wishes to keep the fish alive and in good condition 

 after the blood has been removed. To the layman this sounds 

 paradoxical since he has been taught since childhood that if the 

 heart of an animal is pierced, life is lost. This is a popular 

 fallacy, however, since the removal of blood from the hearts of 

 rabbits and guinea pigs has been a common practice in bacterio- 

 logical laboratories for many years.^ The same technique of 

 taking blood samples from the hearts of dogs has been widely used 

 by the Stanford phj^siologists.- We have extended this technique 

 to rats and swine and used it very extensively during the past 

 three years upon both these species and dogs. That the operation 

 is totally painless is shown by the fact that both dogs and rats 

 frequently rebel when the needle touches the skin but never move 

 when the heart is pierced. Fish, likewise, object to being taken 

 from the water and placed upon their backs but never seem to 

 mind the withdrawal of blood from their hearts. 



By cardiac puncture or ''heart stabbing" we are thus able to 

 ohtain sufficiently large blood samples for many types of analyses. 

 This opens unusual opportunities to the biochemist. This is of 

 special importance since we can employ cold blooded animals whose 

 physiology is somcAvhat simpler than the higher warm blooded 

 species, to obtain fundamental information that may be applied to 

 reactions among the higher vertebrates. 



For the purpose of taking blood from fish we have employed 

 ordinary hypodermic syringes of capacities ranging from two to 

 thirty cubic centimeters, about one ounce. A small syringe is 

 preferable. We have used various sizes of hypodermic needles 

 ranging from %'' in length to l^/i". AVe prefer 19 gauge although 

 larger needles can be used. In order to prevent clotting we have 

 employed either mineral oil or one of the common salts as sodium 

 citrate. When later analyses are not concerned with fat determin- 

 ations upon the blood, mineral oil is the most satisfactory. Both 

 the needles and syringe can be well coated with oil. After removal 

 from the animal the blood is placed quickly into a graduated cen- 

 trifuge tube, containing some crystals of oxalate or citrate. As 



^ Kolmer, Injection, Immunity, and Biologic Therapy. 

 2 E. W. Schultz, Journ. Biol. Chem. (1924) Ix 189. 



