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1910.] Sickness studied by Precise Enumerative Methods. 191 
reddish .débris (stained Giemsa). Many of these vacuolated mononuclear 
cells were of great size (30 to 40 microns in diameter). We are inclined to 
think that this vacuolation with reddish stained débris may be an indication 
of the ingestion of trypanosomes, although we have never observed any 
definite trypanosome structure within them. 
F. W. Andrewes, in the Croonian Lectures,* points out that an intra- 
venous injection of bacteria causes a temporary diminution in leucocytes, 
followed by a marked increase, this fall and rise being chiefly due to 
the so-called polymorphonuclears, the mononuclears taking little part in the 
phenomenon. In this disease, as in malaria, it would appear that there is 
a diminution followed by an increase, chiefly of the mononuclears. This 
tends to suggest that the polymorphonuclear leucocytes react chiefly to 
bacterial infections, while the mononuclears would seem to react chiefly to 
protozoal blood infections (D. T.). 
It is interesting to note that on May 20 there was a very marked mono- 
nuclear increase, coincident with a fall of trypanosomes, and accompanied by 
a remarkable improvement in the clinical condition of the patient; and again 
on June 24 the mononuclear excess changed into a very marked polymorph 
excess. This was coincident with the onset of pleurisy and pneumonia, from 
which the patient died. 
In connection with the leucocyte cycle, the highest numbers recorded were 
50,000 per cubic millimetre of blood, whereas the lowest was 2,800 per cubic 
millimetre of blood. In the latter part of the chart the leucocytic graph 
is altered by the injection of leucocytic extract, and by the development 
of an abscess and pneumonia. 
The following quotation from the Sleeping Sickness Bulletin, 1908, No. I, 
p. 5, is of interest :—“ Dr. W. Thomas found that after an injection of atoxyl 
a change in the parasites became noticeable between the fourth and the fifth 
hour. They became sluggish and much altered in appearance, and at the 
same time there was a noticeable increase in the leucocytes. About the 
seventh hour there was a great diminution in the number of trypano- 
somes, and a coincident increase in the leucocytes, notably the phagocytes. 
At the eighteenth hour parasites were absent and could not be found, even 
after blood centrifugalisation, Instances of phagocytosis were observed 
on these occasions.” 
Thomas and Breinl tried the effect of hyperleucocytic agents without good 
effects, but remark: “It is quite evident that the leucocytes play a role in 
the decrease of parasites.” 
We think that it is possible that on some occasions, at least, Thomas may 
* ‘Lancet,’ July, 1910. 
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