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90 enormous increase, a positive leucocytosis, the normal 8,000 per c.mm. rising to 10,000, or even to 30,000 the proportion to red corpuscles rising from the normal 1 in 500 or 600 to 1 in 300, or even to 1 in 70.

The cause of fever and of periodicity in malaria.—— The cause of fever in malaria is some toxin or toxins liberated when the segmented parasites break up in the blood. Rosenau and others, by injecting filtered blood-serum procured during the cold stage of an ague, have succeeded in demonstrating the presence in the blood of such a substance. The cause of the periodicity is doubtless of a two-fold character, the first and most important being the more or less fixed life-span of the parasites, and the second some physiological property in the human body which tends to destroy the parasites. Like so many physiological phenomena, this malaria-destroying principle or force has a tendency to quotidian increase and decrease. Although sometimes almost powerless to cope with the parasites, it usually brings about, especially after repeated infections, a more or less complete immunity. It might be urged that though such an explanation may be applicable to quotidian periodicity, it could not apply to tertian or quartan periodicity. This cannot be admitted. If there be a regular quotidian occurrence of susceptibility to the malaria germ, this susceptibility must be existent on the second and third day as well as on the first there- fore a tertian parasite, on maturing, will encounter it on the second day, and a quartan on the third, just as certainly as if they were daily-maturing parasites. This hypothesis may be a wrong one. But it will not be without its use if it impress the importance of placing malarial patients under tonic influences as an aid to specific treatment; and of protecting the subjects of malarial recurrences from debilitating influences. For, just as tonic influences may suffice to cure a fever, so, in many malarials, depressing influences are sufficient to provoke relapse: presumably by weakening the physiological element which holds the infection in check.