397 
II. CONTINUANCE OF THE PERIODICAL CYCLE 
The cycle recorded by us till April 30 in our previous paper 
continued till his death. From February 22 till June 25 there 
occurred nineteen rises in the numbers of trypanosomes in his 
peripheral blood. This gives an average of six* and a half days 
between the heights of each rise. 
The shortest period between two successive heights is four days, 
as recorded between April 18 and 22, and again between June 3 
and 7. This exceptionally short interval was due, we think, to 
artificial means, as we shall explain later under vaccine treatment. 
The longest period recorded between two successive heights is 
eight days, while the usual period between the heights seems to be 
seven days. It will be observed that the rise and fall is sudden, 
and that the height is not maintained. 
While the number of the parasites was increasing rapidly, we 
observed many forms with double nuclei and blepharoplasts 
(dividing forms). During the interval between the rises, few of 
these forms were present. This would seem to indicate that the 
sudden rise is due to an active multiplication of the parasites. 
On April 28 the numbers increased from 200 to 1,536 in 
twenty-four hours, and on June 19 they increased from 100 to 1,500 
in twenty-four hours, suggesting that in our patient they were 
capable of dividing and sub-dividing three to four times in 
twenty-four hours. 
The natural fall is even more sudden than the rise. On April 
29 the parasites fell from 1,536 to 100 per cubic millimetre of blood 
in twenty-four hours. 
Except on April 5 and 6 only one observation was made daily, 
so that obviously we may have missed the highest points reached 
in the various rises. The low levels were, as a rule, maintained for 
three or four days, forming U-shaped bends as recorded in the 
chart. The lowest number recorded was 8 per cubic millimetre ol 
blood, while the highest reached 1,536 per cubic millimetre of 
blood. 
It is worthy of note that there is a tendency for a high rise to 
be followed by a low one. This is not without exception, but the 
three highest rises recorded were followed by the three lowest rises. 
