XV] PERIPHERAL GANGLIA AND NERVE CELLS 117 



The sheath of the ganglion consisting internally 

 of several membranes, and externally of loose connective 

 tissue. 



2. Sections of a spinal ganglion (potassium bichro- 

 mate ; cut frozen). Stain a section in hsematoxylin 

 (or in this and eosin also) and mount in balsam. 



Note around each nerve cell the numerous nuclei 

 of the capsule. 



3. Sections of spinal ganglion (mercuric chloride) given in 

 paraffin. Take two cover-slips, fix sections to them, and treat 

 them for staining on the cover-slip (Less. vi. 5) up to the 

 stage of placing them in 50 p.c. alcohol. 



a. Place one slip in Nissl's methylene blue (cp. App. p. 310) 

 for about 20 minutes (or warm it with the solution in a watch- 

 glass, till the fluid begins to steam). Blot it between folds of 

 blotting-paper to remove excess of fluid ; place it before it dries 

 in a mixture of 10 parts aniline oil and 90 parts 95 p.c. alcohol. 

 Gently move it about in this, till the blue colour of the section 

 is rather faint (the proper tint can only be told by trial) ; then 

 blot, transfer to absolute alcohol for 10 to 30 seconds and blot. 

 Clear in xylol, mount in balsam, taking care that the balsam is 

 added to the cover-slip before the xylol evaporates and the 

 sections become dry. 



Note in the nerve cells the basophil masses and granules 

 stained deep blue; they vary in number and size in different 

 cells, and are often absent from the peripheral zone ; they are 

 for the most part arranged concentrically around the nucleus. 



b. Place the other slip for 1 to 1| minutes in erythrosin (cp. 

 p. 310) or eosin, blot, and treat as in a. The erythrosin stains 

 the parts of the sections left unstained by methylene blue. 



Methylene blue in 75 p.c. alcohol or Loffler's methylene blue 

 may be used instead of Nissl's methylene blue ; 95 p.c. alcohol 

 may be used instead of aniline oil and alcohol, but this is apt 

 to produce somewhat diffuse staining. 



