296 



So tfiat by determining these three periods we 

 were able to conclude that the parasite was the 

 malignant tertian. 



In order then to determine the cycle of a 

 parasite it is, necessary : — 



1. To estimate the size and percentage of 

 parasites of each size at any particular time, e.g., 

 starting with the onset of the attack. 



2. To follow each group to its period of 

 maximum development in the circulation. 



3. To estimate the time between this period 

 and the next appearance of young forms. 



4. To estimate the time between the appear- 

 ance of an outburst of young forms (No. i) 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 cateful 

 observation to separate the different groups, 

 though in this particular case the process is facili- 

 tated by the presence of segmenting and pre- 

 segmenting 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 coti- 

 siderable variations may otherwise escape obser- 

 vation. 



