290 Proceedings of Royal Society of Edinburgh. [sess. 
and the slide was placed in an incubator at blood beat, supported 
on two matches over a piece of damp blotting-paper, and left, 
generally, for half an hour. For making several experiments we 
mixed a larger quantity of blood and saline in a warmed glass cell, 
then measured a quantity (up to the mark 1 on the leucocytometer) 
on to each slide to be inoculated. After a slide bad been incubated 
for the required time the edges of the cover-glass were moistened 
with a needle dipped in normal saline solution. The cover-glass 
was then slipped off, and from it and the slide several films were 
made. After trying many methods we found Gulland’s (6) 
formalin-alcoliol method of fixing, and eosin and methylene-blue 
staining, to give us by far the best definition of both cells and 
organisms. A necessary preliminary observation was to note the 
effect on the leucocytes of incubating blood along with an equal 
quantity of normal saline solution alone. On carefully comparing 
films made from the incubated mixture with ordinary films of the 
same blood, we found that the white cells remained practically 
unchanged for two hours. After that period the experiments 
became unsatisfactory, owing to drying of the blood. To exclude 
errors of technique, in every case we prepared ordinary blood films, 
and also films made from the blood incubated with saline solution 
only with those made from inoculated blood. We made experi- 
ments with a variety of organisms, and found that, while as regards 
chemiotaxis and phagocytosis the results were very different, 
leucolysis was always caused, though the extent of the changes 
varied considerably. 
Normal blood incubated with Staphylococcus pyogenes aureus at 
98 '4 F. for thirty minutes. 
Polymorphonuclear leucocytes . — -The great majority of these 
contained organisms. The numbers in each cell varied from one to 
forty or fifty. In parts of the film the only organisms to be seen 
were within the white cells, evidence apparently of chemiotaxis. 
Whether containing organisms or not, nearly all the polymor- 
phonuclear cells showed marked changes. The first stage which 
seems to occur is vacuolation of the protoplasm and faint staining 
of the granules. A second stage is then reached, in which the 
