178 THE FROG ch. x 



b. Tease up a fresh spinal (Fig. 54, B) or sympatlietic ganglion in salt- 

 solution, and stain with methyl-green. Compare the form of the nerve- 

 cells with those in the spinal cord. Sketch. 



c. Cut off a very small piece of any fresh nerve {e.g., sciatic), and 

 tease it out carefully, in a longitudinal direction, in salt solution. Note 

 that it is made up of cylindrical, unbranched nerve-fibres, bound together 

 by connective tissue. 



Examine a single fibre under the high power (Fig. 54, A), and make 

 out the neurilemma, the medullary sheath, and the nodes : at the nodes, 

 the neuraxis can also be seen. Sketch. 



Tease out another piece of fresh nerve in chloroform, so as to partially 

 dissolve the medullary sheath, and note the central neuraxis. Sketch. 



Tease out in glycerine a piece of nerve which has been treated with 

 a I per cent, solution of osmic acid in water for an hour or two and 

 then well washed in water. The medullary sheath will appear nearly 

 black, and the neurilemma, with its underlying nuclei, as well as the 

 nodes, can be plainly seen. Sketch. 



Reflex Action. The experiment described on p. 169 should be 



