408 Collection and Preservation of Parasitic Worms 
of contraction, they are left in a dish of the solution for a longer or shorter 
time, according to size. 
Dr Meggitt is of the opinion that fixatives for cestodes should be used cold, 
as heat tends to make the specimens brittle. The fixative most strongly 
recommended by Dr Meggitt is Zenker’s fluid (corrosive sublimate, 5 grms.; 
glacial acetic acid, 5c.c.; potassium bichromate, 2 grms.; distilled water, 
100 c.c.). After dipping three or four times, as recommended above, the worms 
are placed in a dish of the fixative for 4 to 24 hours, after which they are 
washed in running water for 24 hours, or in iodised 70 per cent, alcohol, as 
described for trematodes. 
Bouin’s fluid (saturated aqueous solution of picric acid, 75 parts; formol, 
25 parts; acetic acid, 5 parts) may also be used, and is better than Zenker’s 
for cvtological purposes, but does not give such straight and extended speci¬ 
mens. It has the advantage that the material may be kept in it as long as 
desired without deterioration. Before examination the specimens should be 
washed in as many changes as possible of 70 per cent, alcohol. 
A simple fixative which, in the writer’s experience, gives fairly satis¬ 
factory results, and is easily made up as often as required, consists of roughly 
equal parts of a saturated watery solution of corrosive sublimate and 70 per 
cent, alcohol, to which, preferably, a few drops of glacial acetic acid should 
be added. (This is roughly Schaudinn’s fluid.) Specimens should remain in 
the fixing bath for ten minutes to half-an-hour, according to size, and are 
then washed in running water for several hours ( e.g ., overnight), or in iodised 
70 per cent, alcohol. They are finally stored in 70-90 per cent, alcohol. 
A modification of this method, useful for rapid treatment of large masses 
of material, is simply to pour over the washed specimens a mixture of 90 
volumes of saturated aqueous sublimate and 10 volumes of glacial acetic acid. 
As a fixative for minute cytological purposes this is not to be recommended, 
but it is sufficiently good for the identification of the material. 
Another method which has been recommended 1 , where minute details are 
not required, is as follows. After being washed in tap-water until they are 
‘‘completely relaxed and dead,” the worms are dropped into a mixture of 
equal parts of pure glycerine, 70 per cent, alcohol and distilled water. The 
mixture is changed as often as it becomes turbid. This method “tends to keep 
the worms soft, and such specimens, after the excess of glycerine has been 
washed out by distilled water, are found to stain very well with Ehrlich's 
acid haematoxylin.” 
In the absence of other reagents, hot or cold alcohol will preserve cestodes 
sufficiently well for identification. Formalin may be used in case of necessity, 
but is not satisfactory, as specimens fixed in it are often difficult to stain. 
For immediate examination of the hooks or eggs, Dr Meggitt uses hot 
absolute alcohol as a fixative, clearing the specimens in xylol as soon as the 
alcohol has become cool. 
1 R. J. Ortlepp (1922), Ann. and Mag. Nat. Hist. (9) ix. p. 603. 
