hæmoglobin, swell up and disintegrate, the hæmoglobin becoming
converted into granules of black pigment inside the parasite. Having
attained a definite size the organism forms a rosette and divides into
a number of forms similar to the smallest seen inside the corpuscles;
these small forms enter other corpuscles and the cycle again begins.
This cycle of development takes place in forty-eight hours, and
segmentation is always accompanied by a paroxysm of the disease shown
in a chill followed by fever and sweating which is due to the effect
of substances liberated by the organism at the time of segmentation. A
patient may have two crops of the parasite developing independently in
the blood, and the two periods of segmentation give a paroxysm for
each, so that the paroxysms may appear at intervals of twenty-four
hours instead of forty-eight (Fig. 20). This cycle of development may
continue for an indefinite time, and there may be such a rapid
increase in the parasites as to bring about the death of the
individual; but with him the parasite would also perish, for there
would be no way of extending the infection and providing a new crop.
The disease has been transmitted by injecting the infected blood into
a normal individual.

[Illustration: FIG. 20.--PART OF THE CYCLE OF DEVELOPMENT OF THE
ORGANISM OF MALARIA, _a-g_, Cycle of forty-eight hour development, the
period of chill coinciding with the appearance of _f_ and _g_ in the
blood. The organisms _g_, which result from segmentation, attack other
corpuscles and a new cycle begins. _h_, The male form or
microgametocyte, with the protruding and actively moving spermatozoa,
one of which is shown free. _i_ and _j_ are the macrogametes or female
forms. _k_ shows one of these in the act of being fertilized by the
entering spermatozoön. The differentiation into male and female forms
takes place in the blood, the further development of the sexual cycle