Sargent, Giant Ganglion Cells of Ctenolabrus. 185 



probable that they have been independently derived from less 

 conspicuous elements as the occasion for great size has arisen. 



Methods. — The brain and spinal cord was carefully removed 

 and immediately fixed in one of the following fluids, — 



(i) 10% solution of Formol. 



(2) Saturated aqueous solution of Corrosive Sublimate. 



(3) Flemming's stronger chromic-osmic-acetic fluid. 



(4) Potassic Bichromate, gradually raised from 2 % to 5 % 

 solution. 



Many stains fail to bring out clearly the giant cells and 

 their neurites though staining other parts of the nervous system 

 well. This is particularly true of the carmine stains. The fol- 

 lowing in the order named proved the most valuable : 



1. Kenyon's Copper Sulphate Phosphomolybdic Acid 

 Hematoxylin, following formol preservation. 



2. Heidenhein's Iron Hematoxylin, used on formol or 

 sublimate material. 



3. Sahli's Methylene Blue Acid Fuchsin Axiscylinder 

 Stain, used on Bichromate material. 



4. Ehrlich's Acetic Acid Alum Hematoxylin double 

 stained with Congo red, or Acid-fuchsin. 



The first stain proved of the greatest value, and as this 

 is the first time, I believe, that it has been used on vertebrate 

 material, deserves a word of comment. Material fixed in 10% 

 formol and preserved in 5 ^ was washed and put in a 5 ^ solu- 

 tion of copper sulphate for 24 hours, by which time it had as- 

 sumed a green color. After cutting in paraffin and mounting 

 in the usual way, they were stained on the slide from 1 5 to 30 

 minutes, in the following : — 



lo^/o Phosphomolybdic acid, . i c.c. 



Hematoxylin crystals, . i gm. 



Chloral hydrate, . . 10 gms. 



Water, .... 400 c.c. 

 They were then rinsed in water, dehydrated, cleared and 

 mounted in the usual way. This is an excellent differential 

 stain for neuroglia, the dendrites of ganglionic cells and espe- 

 cially the axis cylinders, the myelin being left wholly unstained. 



