2674 Journal of Applied Microscopy 



The Technique of Biological Projection and Anesthesia of 



Animals. 



Copyrighted. 



XXI. DIRECTIONS FOR DEMONSTRATING BY PROJECTION THREE IMPOR- 

 TANT PHENOMENA OF THE CIRCULATORY SYSTEM— Concluded. 



A. 2 he circulation of blood in the tail of a fish : 



This instructive experiment is best performed with small goldfish or silver- 

 fish measuring from two and one-half to three inches in length, as they require 

 smaller and lighter cells than larger specimens. The fish is first anesthetized 

 in chloretone solution (see article XII of this series, March, 1903), and is then 

 placed in a suitable cell (Fig. 9, No. 14, or one similar to No. 16, but larger), 

 filled with the anesthetizing solution. It is not necessary that the cell should be 

 large enough to contain the entire fish, butthe tail-fin must be immersed in liquid 

 during projection to prevent its being burned, and should be spread out in con- 

 tact with the front side of the cell so as to be within reach of objectives of medium 

 power. The head of the fish may be held up on one end of the cell by spread- 

 ing the pectoral fins across the top of the cell, or in any other convenient manner. 

 Low power objectives should be used. The special advantage for the study of 

 the circulation afforded by the tail-fin of a fish is seen when the arterioles and 

 venules near the capillaries are observed. These veins and arteries are seen to 

 be parallel to each other and to the fin-rays and the flow of blood from an artery 

 through the capillaries into a vein is more easily traced than in tadpoles or frogs. 

 It will be noticed that the arteries lie close to the fin-rays. The repeated divis- 

 ions of the fin-rays and their articulations are also points of interest worth noting. 



21ie circulation of blood in the web of a frog' s foot : 



Examine the webs in the feet of the frogs which are available for the exper- 

 iment and select one with a thin and light colored web. Anesthetize the frog as 

 directed in article XIV (May, 1903). There are only two points in the demon- 

 stration that are likely to be difficult. First, the frog's web must be fully spread, 

 and, second, the web must be immersed in water during projection. To spread 

 the web take a piece of annealed copper wire about one-thirty-second of an inch 

 in diameter and bend it into the form of a wide hairpin. Bend a half inch at 

 each end of the wire back upon itself so as to form a narrow loop. Hold this 

 spreader against the back of the frog's leg, slip the extremity of one toe into one 

 loop and press the loop together tightly enough to hold the toe securely, and repeat 

 the operation with another toe, either the next one or the second from the first. 

 Now carefully bend the spreader so as to fully spread the web, being careful not to 

 tear it. Keep the web moist while preparing it, and wrap the entire frog, except 

 the foot bearing the spreader, in a moist cloth. The web is now ready to be 

 immersed in water. The best cell to use is one having an opening at the top 

 about one inch by one-half inch in area (Fig. 9, No. 17). Attach the cell to an 

 adjustable frog plate or to a thin board having a hole one inch in diameter cut 

 near one end. A strip of surgeon's rubber adhesive plaster will be found very 



