NUCLEAR STAINS. 29 



into ^ p. c. Acidulated Alcohol till permeated by the acid, 

 placed for a day in 90 p. c. Alcohol, and finally saturated with 

 Absolute Alcohol before embedding. 



NERVOUS SYSTEM. 



Sections of spinal cord which has been hardened in Alcohol, 

 are generally placed in Beale's Ammonia Carmine for two or 

 three days, washed in 90 p. c. Alcohol, cleared, and mounted 

 in Balsam. Much better staining however is obtained by 

 using a stronger Carmine Solution, such as Lithium Carmine 

 or an Ammonia Carmine five times the strength of Beale's 

 Solution, q.v. Sections are stained in this for 24 hours and 

 washed either in 90 p. c. Alcohol, or 70 p. c. Alcohol acidu- 

 lated with yV p. c. Hydrochloric Acid. They may also be 

 stained in either of the Alum Combinations as mentioned 

 below. 



When the central nervous system has been hardened in 

 Chromates, a very prolonged immersion in Ammonia Carmine 

 Solution is necessary, but in order to obviate this delay the 

 following plan (due to Merkel) may be adopted : 



Sections are first placed in a solution of Chloride of Pal- 

 ladium (1 in 500) till they are of a straw colour (about 10 

 1 5 minutes) ; rinsed in Distilled Water ; stained in the Ammonia 

 Carmine Solution (where they quickly become an intense red), 

 washed in 90 p. c. Alcohol, dehydrated, cleared, and mounted 

 in Balsam. The medullary sheaths are stained yellow by the 

 Palladium Solution, while the Carmine stains the neuroglia, 

 axis cylinders, and ganglion cells a deep red. 



Sections hardened either in Alcohol or the Chromates are 

 advantageously stained in Alum Carmine or Alum Cochineal. 

 Both of these solutions stain much more rapidly than Ammonia 

 Carmine. The colour approaches to a violet, and is quite 

 distinct from the red of Ammonia Carmine. 



