752 THE ANIMAL PARASITES OF MAN 



The chief Iron-Hmmatoxylin Stain is that devised by Heidenhain. 

 Unfortunately the procedure involved is a long one, and various 

 modifications have been made to obviate this disadvantage. Haema- 

 tein maybe used instead of ripened haematoxylin. 



One efficacious modification of Heidenhain's stain is that of 

 Rosenbusch. The smear or tissue, after fixation, must be graded 

 downwards through the alcohols to water. Mordant for one and a 

 half hours in a 3^ per cent, aqueous solution of ferric ammonium 

 sulphate. Stain for about three minutes in i per cent, solution of 

 ripe haematoxylin or haematein in absolute or 96 per cent, alcohol, 

 to which a drop of saturated aqueous solution of lithium carbonate, 

 sufficient to produce a wine-red colour, has been added. Differentiate 

 under the microscope with a very dilute solution of the ferric 

 ammonium sulphate. Wash, gradually dehydrate, clear and mount 

 in balsam. It must be remarked that iron-haematoxylin is a regressive 

 stain, hence great care must be exercised in differentiating with the 

 iron alum. 



Gentian Violet. A i per cent, alcoholic solution of gentian violet, 

 or of methyl violet, or of crystal violet, will be found useful for stain- 

 ing spirochaetes. 



Methyl Green. This substance is considered to be a chromatin 

 stain, for either fresh or perhaps recently fixed tissues. A concen- 

 trated aqueous solution contains about i per cent, of the stain. This 

 should be added to a i per cent, solution of acetic acid. It may 

 be used for demonstrating the nuclei of ciliates. 



In conclusion it is essential to remember that the actual magnifica- 

 tion of figures of Protozoa should be given, and not merely the 

 combination of objective and ocular that has been used, for unless 

 the tube-length and distance of the drawing board from the ocular be 

 also given, it is not possible to compute the magnification from such 

 information. Drawings should always be made with the aid of 

 a camera lucida, drawing prism or other form of projection apparatus. 



