TRYPANOSOMIASIS EXPEDITION TO SENE GAMBIA 
3 
Films were fixed either by absolute alcohol or by the vapour of the following 
mixture, in which preparations were allowed to remain for from five to fifteen 
seconds, as recommended by Plimmer and Bradford.* 
Two per cent, solution Osmic Acid | 
Glacial Acetic Acid - - -J ^ U3 P ar s * 
We found the latter to be the better fixative. Its results were more constant, 
anil the minute structure of the parasites, particularly the chromatic granules, were 
better preserved. 
All blood films, except where it is otherwise stated, were stained by the 
following modification of Romanowsky's stain, suggested by Dr. MacConkey :— 
Solution A. Medicinal methylene blue (Hoechst) 0*5 gramme 
Sat. solution of chemically pure borax in dis- 
tilled water - - - - - 50*0 c.c. 
Incubate for four days at 37 J C, then add absolute 
alcohol ______ ^o'O c.c. 
and allow to stand for one day before using. 
Solution B. Eosin, extra B.A. crystal (Hoechst) 0*25 gramme 
Distilled water _____ <;croo c.c. 
Absolute alcohol _____ ^croo c.c. 
These are the stock solutions. For laboratory use dilute each with distilled 
water, one part of stain to nineteen of water. Support the slide to be stained face 
downwards. Mix equal parts of the diluted stains in a small flask and pour 
immediately into the staining dish. The length of time necessary for staining vanes 
from three to six minutes. 
When staining is complete, wash the specimen quickly but thoroughly in water 
and allow it to dry in the open air. 
The quantitative estimations of blood cells were made with the Thoma- 
Zeiss ' blood counting apparatus.' A Zappert ruled cell was used, and both erythro- 
cytes and leucocytes were estimated from the same preparation. The haemoglobin 
was estimated with a Fleischel's haemoglobinometer. 
The qualitative leucocyte counts were made almost wholly from slides stained 
by the above-mentioned modification of Romanowsky's method. When it was 
considered necessary to corroborate the results obtained by these methods, slides fixed 
by heat and coloured with Ehrlich's tri-acid mixture were also examined. 
In order that our tables of differential leucocyte counts may convey a real 
meaning we have thought it well to define as exactly as possible what are the charac- 
teristics which have determined the headings under which we have classified the 
leucocytes. Cells having one of the three recognized types of granulation, as described 
* Plimmer and Bradford, S^uwt. jour. mic. science, Vol. XLV, part iii. 
