27 STAINING Ad K -V TS. 



Eosin. 



This is a valuable general stain, as it has a great coloring 

 capacity. It stains nucleus and cell wall readily and is much used 

 in double staining. It can be applied either in an aqueous or alco- 

 holic solution ; 1 gram of eosin to 100 c.c. of water is a very con- 

 venient strength. 



Haematoxylin. 



This coloring agent can not be recommended too highly. It 

 has a very wide application and gives uniformly good results. The 

 stain is made by adding a concentrated solution of haematoxylin 

 crystals in alcohol, cautiously, to a 3 per cent, aqueous solution 

 of alum, until a medium purple color is obtained. The solution 

 becomes darker and better by standing a few days, but deteriorates 

 after a time and will require filtering often. As suggested by Prof. 

 Gage the addition of chloral hydrate and proper sterilizing of the 

 constituents of the stain during its manufacture greatly increases 

 its keeping power. (Proc. Am. Microscopical Society, Jan. 1893). 



The old stain, if kept in a cool place, is very valuable in stain- 

 ing meristematic tissue. Haematoxylin stains the nucleus a deep 

 blue or purple and is to be recommended for all general work. It 

 is sometimes used in staining bacteria and with other stains in 

 double staining. 



ANILINE COLORS. 



These colors have of late been very useful in furnishing stains 

 for histological work. To them we owe much for the present valu- 

 able and convenient methods of staining. Only a few of the more 

 important agents can be included in this outline. 



Hethyl Violet. 



An aqueous solution of this is much used in staining bacteria. 

 It is also valuable as a selective stain for many plant tissues. 



riethyl Green. 



An aqueous solution with 1 per cent, of acetic acid is used for 

 staining the nucleus and chlorophyll grains. As a double stain it is 

 often used on transections of stems in connection with eosin. 

 Iodine green is, however, preferable for double staining. 



