582 PROTOZOA 



three to five minutes, drain and stain in excess of haeniatoxylin 

 for the same time. Wash and differentiate in very weak solution 

 of ferric chloride (0-25 per cent.). Wash well in tap-water to stop 

 decolourisation at the correct moment as determined by examining 

 under the microscope. 



Chromatin dark blue, fibrin greyish, red blood corpuscles (after 

 fixing in Zenker), greenish-grey, connective tissue tinted pale 

 yellow. 



(c) Weigert's iron-haematoxylin mixture, in which the mordant 

 is already mixed with the stain (§ 284) affords a rapid method, 

 requiring only a few minutes and no differentiation. Dobell 

 and O'Connor find it specially good when the protozoa are more 

 or less imbedded in mucus. 



{d) Dobell's alcoholic iron-haematein method {Arch. Protistenk., 

 xxxiv, 1914, p. 139) requires only a short time. Transfer films 

 or sections from 70 per cent, alcohol into 1 per cent, iron alum 

 in 70 per cent, alcohol and leave them to mordant for ten minutes, 

 rinse in 70 per cent, alcohol and place in 1 per cent, haematein 

 in 70 per cent, alcohol for ten minutes. Differentiate in iron-alum 

 solution or acid alcohol (70 per cent, containing 0-6 per cent. HCl). 

 Then wash in several changes of 70 per cent, alcohol. 



This stain, though good for chromosomes, is said by Dobell 

 to be unreliable for staining cysts owing to unequal penetration. 



(e) Delafield's haematoxylin (see § 295) is a good stain for 

 protozoa mounted whole. 



Transfer films and sections from distilled water into a very 

 dilute, slightly acidified, solution of the stain. For progressive 

 staining five or ten minutes is generally enough (or the prepara- 

 tion may be treated regressively, i.e. overstained by leaving 

 longer and differentiated in 0-5 per cent. HCl in water). The 

 preparations will be pink. Wash until blue, i.e. alkaline, in 

 tap-water. Assuming that the tap-water is alkaline ; if not, a 

 trace of sodium bicarbonate may be added to it. 



N.B. — ^Care should be taken that the clearing and mounting 

 media are quite neutral. Any acidity will, of course, turn the 

 preparation red again and in time decolourise it. 



(/) Ehrlich's haematoxylin (acid) (see § 296) is also useful 

 for protozoa and tissues. Use pure, undiluted, otherwise proceed 

 as for Delafield's stain (see above). 



(g) Mayer's haemalum (see §§ 288 and 289), recommended by 

 Dobell {Amoehce in Man. 1919, p. 6) as a i-eliable and rapid 

 stain for cysts of protozoa, should be a deep red colour ; when 

 it turns brown and precipitates, it is no longer fit for use. Transfer 

 films or sections from distilled water to the stain for five to twenty 

 minutes, then wash and mount as described above for Delafield's 

 haematoxylin. 



{h) ^L\YER's glychaemalum (see § 291) is similar to Ehrlich's 



