but as the parasite is completely inclosed in the corpuscle
wall these waste products cannot escape until the wall bursts open.
After about forty hours if the parasite is _vivax_ or about sixty-five
hours if it is _malariae_ it becomes immobile, the nucleus divides again
and again and the protoplasm collects around these nuclei, forming a
number of small cells or spores, as they are called. In about
forty-eight or seventy-two hours, depending on whether the parasite is
_vivax_ or _malariae_ the wall of the corpuscle bursts and all these
spores with the black pigment and the waste products that have been
stored away within the cell are liberated into the blood-plasm.

[Illustration: FIG. 99--Diagram to illustrate the life-history of the
malarial parasite. 1 is a red blood-corpuscle, 2 to 7 shows the
development of the parasite in the corpuscle, _a_ _b_ _c_ _d_ and _a'_
_b'_ _c'_ and _e_ the development of the parasite in the stomach of the
mosquito, _f_ _g_ _h_ _i_ the development in the capsule on the outer
wall of the stomach of the mosquito, _k_ in the salivary gland.]

[Illustration: FIG. 100--Malarial mosquito (_A. maculipennis_) on the
wall.]

[Illustration: FIG. 101--Malarial mosquito (_A. maculipennis_) standing
on a table.]

These spores are round or somewhat amoeboid and are carried in the
blood for a short time. Very soon, however, each one attacks a new red
corpuscle and the process of feeding, growth and spore-formation
continues, taking exactly the same time for development as in the first
generation, so every forty-eight hours in the case of the _vivax_, and
every seventy-two hours in the case of the _malariae_ a new lot of these
spores and the accompanying waste products are thrown out into the
blood. Thus in a very short time many generations of this parasite occur
and thousands or hundreds of thousands of the red-blood corpuscles are
destroyed, leaving the patient weak and anemic. It will be seen, too,
that the recurrence of the chills and fevers is simultaneous with the
escaping of the parasites from the blood-corpuscles, together with the
waste products of their metabolism.

These waste products are poisonous, and it is believed that this great
amount of poison poured into the blood at one time causes the regular
recurring crisis. Zooelogists well know that this process of asexual
reproduction, _i. e._, reproduction without any conjugation of two
different cells, cannot go on indefinitely, and th