AND THE PROPAGATION OF DISEASE). The para site develops after its introduction into the blood and, according to the individual type that is introduced, certain variations in the develop mental history of the disease result. The para sites themselves, which are thought to be low forms of animal life, protozoa, develop, for the most part, in the red blood-corpuscles and have many allies in the red blood-corpuscles of other animals, as frogs, fish, birds, monkeys, cats, etc.
These organisms were first clearly demon strated by Laveran, a French army surgeon, in 1880, and his early observations were enlarged and amended by Golgi, Marchiafava and Celli, Manson and Ross, and a host of others. At the present time at least three forms of the parasite Hwmatozoa malaria. are known, the parasite of tertian fever, the parasite of quar tan fever and the parasite of estivo-autumnal fever. These parasites have two cycles of de velopment, one taking place in the body of man and the other in the body of the mosquito. Thus a patient with malarial fever infects a mosquito with a parasite which undergoes cer tain transformations within the body of the mosquito, and is then in turn introduced into the body of another patient, to cause typical attacks of fever according to the type ofpara site introduced. Occasionally two different parasites are introduced into the patient's body and a mixture of the two forms of the disease results.
The commonest form of malarial fever (the so-called chills and fever, or ague) is due to the tertian and quartan parasites. In these, after an unknown period of incubation, probably from 36 hours to 15 days, the patient has a feel ing as though he were going to be sick, some times with headache, sometimes a feeling of lassitude and a desire to yawn and to stretch. Occasionally the patient has nausea and vomit ing. At the same time the temperature has be gun to rise and a chill commences. He begins to shiver, the face becomes drawn, thin and cold, the body shakes, the teeth chatter and the skin may be cold and blue, although the internal temperature is known to be gradually rising. After from 10 to 15 minutes, or perhaps a longer time, the chill is followed by a hot stage. The coldness of the surface disappears and the face becomes congested and flushed, the skin is red, the pulse is full and the patient may have a throbbing headache, with mental excite ment. Thirst is excessive. Then the period of
sweating begins, the whole body being covered with perspiration; the temperature drops, the headache disappears and in an hour or two the paroxysm is over.
A number of variations from this typical form are known. In the tertian type of fever the chill and fever usually occur every other day. This is due to the fact that the cycle of development of the tertian parasite is about 48 hours and that the stage of full development of the parasite, or sporulation, which is more or less coincident with the attack, occurs at these times. Thus every third day the patient has an attack, hence the term ttertian.* In the mixed infections, when two sets of parasites develop on alternate days, the paroxysms of chills, fever and sweating may occur every day. In the quar tan type of fever the cycle of development of the parasite is completed every fourth day. Mixed infections also occur in this form of the disease. In the northern United States these are the types of malaria which are more com mon, but below Mason and Dixon's line a much severer form of the disease is present. This is the iestivo-autumnal type, which gives rise to the so-called bilious remittent fevers and typho malarial fevers of the South. In these the symptoms are extremely irregular. The par oxysms occur every 24 or 48 hours, and longer remissions are known. The length of the par oxysms is usually longer, lasting 20 hours, in stead of 10 or 12 as in the tertian form; the onset of the disease is usually slow and gradual; and there may be no chill. Occasionally there is a continuous fever without much break, the temperature ranging from 102° to 103° F. Jaundice is not infrequent, and this, with the fever and a furred tongue and mental disturb ance, often gives rise to the suspicion of typhoid fever. In the simpler types the patient may get well after 10 days or two weeks without any special medication. The more severe forms may be fatal unless prompt diagnosis and medi cation are instituted. The diagnosis of mala ria should always include an examination of blood and the demonstration of the parasite. In the vast majority of untreated cases the parasite can be found. Occasionally, however, repeated examination fails to show it.