2 3 6 



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 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. i. (? 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. 



