236 
of an outburst of young forms (No. 1) and a second 
similar outburst (No. 4). 
The interval between one and four should be 
equal to the sum of the intervals of periods two and 
three. It is more accurate to use a micrometer scale 
for measuring, but the estimation can be made with 
considerable accuracy without. 
If we are dealing with three generations of 
parasites as in a triple quartan the principle is precisely 
the same, though it may require careful observation 
to separate the different groups, though in this par¬ 
ticular case the process is facilitated by the presence 
of segmenting and presegmenting bodies which are 
easily counted. In order then to establish a parasite 
cycle, repeated observations at definite intervals are 
necessary, and also the temperature should be carefully 
recorded every four hours or two hours as considerable 
variations may otherwise escape observation. 
Quotidian 
Parasites have been described which complete 
their development in twenty-four hours (about). 
Thus, at the pyrexia young forms occur. During 
the apyretic interval large forms and presegmenting 
forms, and, again, at the next attack young forms, 
thus developing in twenty-four hours. As we have 
stated above, to establish accurately this cycle three 
periods would have to be traced :— 
No. 1. (? Twelve hours) from young forms to 
largest forms. 
No. 2. (? Twelve hours) from largest forms to 
young forms. 
No. 3. Twenty-four hours from young forms to 
young forms. 
