8 PEACTICAL PAEASITOLOGY 



potassium iodide 6, iodine 4), has been added to make it the colour of 

 port wine. Specimens are allowed to remain in this until they begin 

 to turn a pale yellow (cover-glass preparations, about a quarter of an 

 hour) ; they are then again rinsed in 70 per cent, alcohol, and are 

 hardened (at least a quarter of an hour) in 80 per cent, alcohol, where, 

 unless they are to be stained or embedded immediately, they should 

 remain for future use. 



Osmic Acid (Lee). A mixture of 2 parts osmic acid in 100 parts 

 of a 1 per cent, chromic acid solution should be kept in readiness as 

 a foundation for F lemming's mixture and for the fixing of cover-glass 

 preparations in osmium vapour. This latter method may be employed 

 for blood parasites and Infusoria (see later, under special heading). 



Acetic Acid Solution of Chromium and Osmium (Flemming). One 

 part of the above osmic acid mixture, 4 parts 1 per cent, chromic 

 acid, 2 parts 1 per cent, acetic acid, 13 parts distilled water. This 

 mixture should not be prepared until it is required for use. It may 

 be employed with advantage for the preservation of blood containing 

 parasites, for cover-glass preparations of certain Protozoa, as well as 

 for small portions of organs containing parasites. It acts upon thin 

 cover-glass preparations and upon blood (the latter should be allowed 

 to drop into the solution) in ten to fifteen minutes ; and upon pieces 

 of organic tissue, which should be as small as possible, in half an hour 

 to one hour. The specimens should be very carefully washed in distilled 

 water, after which they are transferred to alcohol, the concentration 

 of which is gradually increased. They are finally coloured with iron- 

 haematoxylin or aniline dyes, or (though this is not so good) with 

 ordinary hsematoxylin or carmine. 



Acetic Acid Solution of Chloride of Platinum and Osmium (Her- 

 mann). Fifteen parts 1 per cent, platinic chloride solution, 1 part 

 glacial acetic acid, 4 parts 2 per cent, osmic acid. To be used instead 

 of Flemming's mixture and in the same way. 



Acetic Acid Solution of Picric Acid and Mercurial Sublimate 

 (Bath). Equal parts of saturated solution of mercuric chloride (see 

 alcohol sublimate) and picric acid (1 per cent, in distilled water), with 

 the addition of | to 1 per cent, glacial acetic acid. Very useful for 

 fixing portions of tissue containing parasites. Specimens should be left 

 in the mixture for several hours, after which they should be washed, 

 first in 50 per cent., and afterwards in 70 per cent, alcohol. 



Picro-formol (Bouin). Fifteen parts saturated watery solution of 

 picric acid, 5 parts formalin (of commerce), 1 part acetic acid. This 

 is said to produce very good results indeed, and is employed in the 

 same way as picrin-sublimate. 



Absolute alcohol is used to fix dry cover-glass preparations (see 

 later, under Examination of Blood). 



