XV] PERIPHERAL GANGLIA AND NERVE CELLS 119 



7. Tease out in formic glycerine a small piece of 

 the spinal ganglion of a skate (ganglion in 30 p.c. 

 alcohol for 3 days, one day in picrocarmine, washed; 

 kept in glycerine). 



Note the bipolar cells, forming oval to spherical 

 nucleated swellings on the course of a nerve fibre. 

 The connective tissue sheath of the nerve will be seen 

 to run over the cell and form its capsule. 



8. Spiral nerve cells of the auricular septum of the frog. 

 Take a pithed frog : expose the heart, cut through the peri- 

 cardium, lift up the edges and cut it away so far as it is seen. 

 Turn the ventricle forward, tie its ligament and cut peripherally, 

 lift up the heart by the ligament and pass two silk threads under 

 the aortoe. Draw one backwards, and tie, the veins running to 

 the heart ; in doing this lift up the ventricle by the ligament and 

 make certain that the auricles are not included in the ligature. 



With scissors make anjncision into the bulbus just before it 

 branches, being careful not to cut it through. Squeeze the heart 

 a little to empty it, wipe away the blood with a piece of sponge 

 moistened with normal salt solution. Put a fine pointed cannula 

 provided with a short piece of india-rubber tubing into the bulbus, 

 prop up the tubing so that the cannula will not slip out, tie it 

 in the bulbus. By means of a pipette fill the cannula with salt 

 solution, squeeze the tubing and so force the salt solution into the 

 heart. Remove the fluid from the cannula by means of the 

 pipette, fill with fresh salt solution, and so on till the fluid 

 returning to the cannula from the heart is colourless. 



Empty the cannula, fill it with -5 p.c. gold chloride, take a 

 glass rod which fits the tubing, and slowly push it in so that 

 the heart is distended with gold chloride. See that the right 

 auricle is distended for a minute or two ; then lift up the heart 

 by means of the cannula and the thread tied round the veins, 

 and cut peripherally of the ligatures. Place the heart in a little 

 gold chloride solution in a watch-glass for half- an-h our. Transfer 

 to water, cut away the bulbus with the cannula, the superfluous 



