THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
possibility of altering their virulencies. We reserve for this report descriptions of 
the microscopical post-mortem appearances in infected animals, and a detailed comparative 
examination of all known pathogenic trypanosomes. 
Laboratory Methods 
Blood was examined, both fresh and stained. When it was possible the 
centrifuge was used in preparing the fresh specimens, which were examined as soon as 
prepared. We found that if trypanosome-infected blood were mixed with equal parts 
of the following solution and centrifuged, the great majority of the parasites were 
collected with the white cells in a thin white layer, which could be easily removed 
with a fine pipette :— Sodium citrate . i gramme. 
Normal saline solution 100 c.c. 
For centrituging the blorxi of animals from which it was possible to obtain 
several cubic centimetres, urine centrituging tubes were used. These were far too 
large, however, for examining the blood of natives, small birds, and animals, of which 
we could obtain only a few drops at a time. For examining such small quantities, 
varying in amount from cr i c.c. to o - 2C c.c, we adopted the following method. 
Rather thin-walled, easily fusible glass tubing, having an internal diameter of five mm., 
was drawn out into bulb-shaped capsules having an arm at either end, and capable of 
being placed in the haematokrit arm of a centrifuge.* Blood was allowed to enter the 
bulb by capillarity, until it was half or three-quarters filled. The sodium citrate solution 
used as a diluting fluid was then allowed to fill up the remaining space, and the bulb, 
its longer arm having being carefully sealed in the flame of a spirit lamp, was placed 
in the centrifuge. 
In fifteen minutes a well-marked white ring is present. The serum and diluting 
fluid can very quickly be removed by gently scratching and then breaking the glass 
about four or five mm. above the ring, and smartly tapping the bulb containing the 
undesired clear fluid. The white ring can then be easily removed by a capillary 
pipette and examined under a coverslip as a moist preparation. 
We nearly always used a one-sixth (Zeiss D) objective with a No. 4 ocular (the 
diaphragm of which had been removed) in searching fresh blood for trypanosomes. 
By doing this we secured a large field, and were able to examine slides very quickly. 
Since a living parasite is always ' spotted ' by its movements rather than its form, we 
lost but little efficiency in so doing. Even with the aid of this manoeuvre, ten to 
fifteen minutes were required to examine the amount of blood covered by a three- 
quarter inch square coverslip, the size which we used throughout our work. 
Blood films on slides were taken from every case for permanent preparations 
and further study. 
* Kanthick, Dmhim, and Blandford, Royal Society Proceedings, vol. lxiv, No. 404, 1898 ; Durham, Thompson Yates 
Laboratories Report, Vol. IV, pt. ii, 1902. 
