168 E. A. MINCHIN. 
contents into capillary glass tubes, from which fine drops were 
expelled by blowing them gently on to slides, in order to make 
the smears. When made, the smears were sometimes dried 
rapidly in the air and then fixed with absolute alcohol or 
methyl alcohol, sometimes fixed with osmic vapour, employed 
in the manner recommended to me by my friend Dr. Plimmer : 
twenty drops of 4 per cent. osmic acid, with one drop of glacial 
acetic, placed in a stoppered tube of sufficient calibre to hold 
a slide, and the wet smear placed into the tube for about half 
a minute. I also tried a modification of this, as follows: A 
drop of blood on a slide was exposed, as rapidly as possible, 
to the osmic-acetic vapour for about half a minute, then mixed 
with an equal-sized drop of equal parts of fresh serum and 
dilute glycerine, and the whole smeared out. Subsequently 
the smear was fixed with absolute alcohol, without letting it 
dry ; the glycerine was used in order to keep it moist for any 
length of time. I found, however, that this method tended to 
shrink the trypanosomes, though successful in other ways. It 
would be necessary to experiment in order to find the exact 
proportion of glycerine that should be mixed with the serum. 
In general I found the form of the body much more perfectly 
preserved in osmic-fixed smears than in air-dried prepara- 
tions; the trypanosomes appear solid and plastic in the 
former, and always more or less flattened out in the latter. 
It seems, indeed, inevitable that the violent method of drying 
must deform a soft protoplasmic body.! 
I wasted, I am sorry to say, a great deal of precious time 
trying to stain trypanosomes by the ordinary technique, which 
gives such good results with other Protozoa, especially the 
various carmine and logwood stains, which all proved useless. 
It is a puzzle to me why the Protozoa parasitic in blood should 
be so entirely different from other Protozoa in their staining 
reactions. I have always experienced just the same difficulty 
in trying to stain other Protozoa by the methods so successful 
for blood parasites. I fell back, finally, entirely upon the 
1 Lithe (26, p. 70), makes some valuable remarks on this point. Compare 
also Plimmer (85). 
