84 
V. JANUARY TO JUNE, 1914 
■ every persistent headache, of every prolonged attack 
of sleeplessness, and of all rheumatic pains must be 
gauged with the help of the microscope. Moreover, 
this examination of the blood is, unfortunately, by no 
means simple, but takes a great deal of time, for it is 
only very seldom that these pale, thin parasites, about 
one eighteen-thousandth of a millimetre long, 
are to be found in any considerable number in the 
blood. So far I have only examined one case in which 
three or four were to be seen together. Even when the 
disease is certainly present one can, as a rule, examine 
several drops of blood one after another before dis- 
covering a single trypanosome, and to scrutinise each 
drop properly needs at least ten minutes. I may, 
therefore, spend an hour over the blood of a suspected 
victim, examining four or five drops without finding 
anything, and even then have no right to say there is 
no disease ; there is still a long and tedious testing pro- 
cess which must be applied. This consists in taking 
ten cubic centimetres of blood from a vein in one of the 
sufferer’s arms, and keeping it revolving centrifugally 
for an hour according to certain prescribed rules, at the 
same time pouring off at intervals the outer rings of 
blood. The trypanosomes are expected to have 
collected into the last few drops, and these are put 
under the microscope ; but even if there is again a nega- 
tive result, it is not safe to say that the disease is not 
present. If there are no trypanosomes to-day, I may 
find them ten days hence, and if I have discovered some 
to-day, there may be none in three days’ time and for a 
considerable period after that. A white official, whose 
blood I had proved to contain trypanosomes, was 
subsequently kept under observation for weeks, in 
