DAHLIA. 69 



In Gram's method the sections are treated, after staining, 

 with a solution composed of 



Iodine ..... 1 gramme. 

 Iodide of potassium . ... 2 grammes. 

 Water 300 



In Bizzozero's adaptation of this process the series of opera- 

 tions is as follows : Stain in the gentian, wash for five 

 seconds in alcohol ; two minutes in the iodine solution ; twenty 

 seconds in alcohol ; thirty seconds in the chromic acid solu- 

 tion ; fifteen seconds in alcohol ; thirty seconds in the chromic 

 acid again ; thirty seconds in alcohol ; and treatment with 

 changes of clove oil until final decoloration. 



NISSEN (Arch. f. mifc. Anat., 1886, p. 338) employs this pro- 

 cess with omission of the treatment with chromic acid. 



In resting nuclei the nucleoli alone are stained, or the 

 chromatin if stained is pale ; in dividing nuclei the chromatin 

 is stained with great intensity, being nearly black in the 

 equatorial stage. 



This exceedingly powerful stain is quite as precise as that 

 of safranin, to which it is perhaps even preferable for much 

 work with very thin sections (thick sections with closely packed 

 nuclei may easily come out too dark). It lends itself admir- 

 ably to double staining with eosin, with which it affords one 

 of the most useful and beautiful double-stains known (see 

 258). 



The stain keeps fairly well in damar, though not so well as 

 that of safranin. Flemming found that after a year it had 

 fadad a little, though not so much as hasmatoxylin stains (v. 

 Zells. Kern. u. Zellth., p. 384). 



Gentian violet in acid solution stains the nuclei of fresh tissues, and dis- 

 solved in indifferent media is sometimes very useful for staining intra vitam 

 (see above, 93). 



- Gentian may be washed out by substitution, whence the important 

 method of Flemming, 258, which see. 



, 103. Dahlia (FLEMMING, Arch. f. mik. Anat., xix, 1881, 

 p. 317). Stain in an aqueous solution, either neutral or 

 acidified with acetic acid, and wash out with pure alcohol. 

 The stain is paler in the nuclei than with gentian or safranin. 

 The cytoplasmic granulations of certain cells are sharply 

 stained. 



