N. H. SwELLENGREBEL 
229 
difficult to decide if the base of the flagellum does or does not reach the 
blepharoplast, sometimes this was evidently the case, in other specimens 
the flagellum near the blepharoplast became suddenly indistinct (Fig. 16). 
The base of the flagellum was often distinctly thickened, so that it 
seemed to end in a granule (Minchin’s blepharoplast). 
The nucleus is round or oval, from one to three little granules are to 
be seen, but no large karyosome as figured by Rosenbusch and Moore 
and Breinl (Fig. la, lc). In one case delicate fibrillae were to be seen 
uniting the central karyosome with the periphery of the nucleus 
(Fig. la). 
Because of the deformation of the cells in the standard preparations 
during the fixation, their size does not wholly coi’respond with Minchin’s 
observations (vide Table II). 
The following technique was used to make “ wet-fixed never-dried ” 
blood films from Mus rcittus infected with Tr. leivisi, the latter not 
being in the multiplication period: 
The drop of blood taken from the rat’s tail was placed on a cover-slip 
and immediately covered by another cover-slip so that the blood spread 
between them in a thin layer. Then the two cover-slips were quickly 
drawn apart and immediately placed (blood film down) on the surface of 
the fixation-liquid and immersed in it after some minutes. The 
manipulation of separating the two cover-slips must be performed very 
quickly to prevent the drying of the thin films. 
The fixation-liquids used were the following: Osmic acid in vapour 
and in solution (2 °/ 0 ) followed by hardening for 24 hours in absolute 
alcohol; weak Flemming’s solution ; Hermann’s solution ; Bonin, Rabl, 
Rath, Schaudinn and Merkel’s fluids; absolute alcohol. To compare 
these methods with the dry fixation method, blood films were dried 
and then fixed in absolute alcohol. 
Dried films as a rule were stained by Giemsa (Grtibler’s solution 
1 cm., dist. water 10 cm.). As a control dried preparations were also 
stained with iron hematoxylin. Preparations fixed wet after Schaudinn, 
Bouin, Flemming etc. were also stained with Giemsa’s stain. With dry 
fixation the staining method was purely progressive, with never-dried 
preparations it was necessary (to mount in cedar oil) to pass them 
through alcohol or aceton-xylol mixtures, consequently differentiation 
was inevitable. To study minute nuclear structures, one must take 
care to stain only for a short time (^—1 hour); to procure preparations 
showing the flagellum well the staining should last longer (1—6 hours). 
It is desirable to ascertain under the microscope from time to time 
Parasitology iii 
15 
