X/X.] STEUCTUEE OF NEEVOUS TISSUES. Ill 



Observe with a low power that 



o. The fibres of the anterior root mix with 

 those of the posterior root below the gan- 

 glion. 



h. Most of the ganglion cells lie outside the 

 fibres of the posterior root ; some lie in rows 

 between the fibres. 



2. Observe with a high power 



a. In the ganglion cells the rather granular 

 cell-substance, containing a large spherical 

 nucleus which often has one or more distinct 

 nucleoli. 



h. The many nuclei of the capsule of each 

 ganglion cell. 



c. The stained axis cylinders of the nerve fibres. 

 (The medulla may show an irregular network 

 of substance hardened by the ammonium 

 bichromate.) 



d. The nerve fibres coiled amongst the cells, 

 and fibres running more or less transversely 

 from the lateral mass of cells to the central 

 bundle of nerve fibres. 



3. Destroy the brain and spinal cord of a frog and 

 cut off its head. Remove the lower jaw and 

 divide the skull in two down the middle line. 

 Tear away the mucous membrane covering the 

 roof of the mouth ; the inner and lower part of 

 the eye will be laid bare. Just behind the eye is 

 a depression ; from this two or three small fila- 

 ments, the branches of the fifth nerve, will be 



