PEOTOZOA 13 



until the protoplasm is a pale grey in colour, to which the chromatic 

 portions of the nucleus, stained a deep blue-black, offer a striking 

 contrast. Very frequently, however (as in the Coccidia of rabbits), 

 it is difficult to distinguish between the granulations of the plasm 

 and the chromatic elements. In such cases it is advisable, after 

 strong differentiation, to re-stain in a weak aqueous solution of 

 Bordeaux red. 



For details of the iron-haematoxylin method, as modified for the 

 purpose of examining Trypanosomes, see chapter on Examination 

 of the Blood. 



The so-called Romanowsky or Giemsa stain is particularly prized 

 for its brilliant colour-tints, but good results are only obtainable 

 where the preparations are allowed to dry after staining. For this 

 reason it is useful only in examining blood, and will be discussed 

 later under that special heading. 



Schaudinn states, however, that he has succeeded in using 

 Komanowsky's stain for wet preparations. The specimens were 

 strongly over-coloured, and the subsequent alcohol treatment, which 

 was performed as rapidly as possible, sufficed to extract precisely the 

 right amount of dye. I must admit that, personally, I have never 

 been very successful with this method. No degree of over-colouring, 

 however intense, would withstand the alcohol treatment necessary 

 to dehydration, and the beautiful Eomanowsky colouring of the 

 nuclei was always destroyed. 



Very varied effects are obtained by staining paraffin sections by 

 Mallory's method. They are first immersed in a $ per cent, solution 

 of acid fuchsin ; then in 1 per cent, phosphormolybdic acid ; and, 

 finally, for five minutes in a solution consisting of aniline blue, 0*5 

 per cent., orange-green, 2 per cent., oxalic acid, 2 per cent., in 

 distilled water. They are then rapidly washed in water, rinsed in 

 96 per cent, alcohol, and are transferred as soon as possible to absolute 

 alcohol and xylol. By this method Vorticelli are coloured as follows : 

 plasma, light orange ; macronucleus, yellow ; contractile vacuoles, 

 brown ; vacuoles of nutrition, blue ; myonemes, bluish ; muscle of 

 stalk, dark blue ; sheath of stalk, light blue ; pellicle and cilia, orange ; 

 surface of the body, grey-blue. Myxosporides are coloured as follows : 

 shells, orange ; spore-plasma and nematocysts, violet ; nucleus, red 

 (0. Schroder). The differentiation is, however, somewhat capricious, 

 and the method for this reason not to be unreservedly recommended. 



The colouring of the living organism with neutral red is a useful 

 method when studying certain more delicate structural arrangements, 

 such as the organelles of metabolism. The stain must be very much 

 diluted a solution of 1 in 10,000 to 1 in 100,000 will be found active. 

 If the Protozoon stains a bright red, acid is present; if the colour 



