THE MODE OF ACTION OF MALARIA.
Malarial poisons being organisms their morbifie action is likely to bear a relation to their reproduction and organic growth. The phenomena of the maladies which they cause are indeed such as can scarcely be explained on any other view. A short residence, even one night, in a malarial district may give rise to a fever of some weeks' duration. If during one night the sufferer inhaled enough poison to cause an attack of fever so prolonged—if the whole of the poison requisite to the production of such an illness existed in and acted on the system at the commencement of the attack, the sufferer should be speedily killed by a dose competent to produce such an illness. Moreover, if the whole of the poison existed in the system at the commencement of the attack not only would the full effects of the poison be produced at once, but malarial fevers would lose their intermittent and remittent character, and their phenomena be con centrated into a violent attack of continued fever in which recovery would be the exception. It does not seem possible to explain the phenomena of these fevers on the supposition that the whole of the poison necessary to their production exists in the system at the time of onset of the malady. Their varying and intermittent course, their prolonged duration, and their small mortality can be accounted for only on the view that their poisons are reproduced during their course, and that this reproduction takes place in an intermitting manner. And the researches of Laveran, Golgi, etc., have demon strated that such is the case, the malarial poison being abundantly found in the blood during the pyrexia and not during the apyrexia.
All organisms exercise a definite action on their environment. The environment of these organisms is the blood and the tissues of the body; and what we have to consider is whether or not their action on this environment would suffice to produce the phenomena of mala rial fever. The special phenomena which have to be considered are : 1. The occurrence of fever; 2. The occurrence of intermissions in this fever.
The action of minute organisms on their environment essentially consists in the consumption of nitrogen and water. The malarial poison, therefore, consumes the nitrogen and wafer of the blood and tissues. But as nitrogen and water are the chief elements required for the nutrition of the tissues such an action must have serious effects on the system.
That the reproduction in the system of minute organisms having such an action is competent to cause the essential phenomena of fever I have elsewhere in the case of the continued fevers shown in some detail.
Increased consumption of water causes thirst, dry skin, and scanty urine. Increased consumption of nitrogen means increased meta bolism, rise of temperature, increased rapidity of circulation, in creased formation and elimination of urea, wasting of the nitrogenous tissues; these are the essential phenomena of fever. The nitrogen and water which ought to go to nourish the tissues are in great part taken up by these minute organisms. Give as much nitrogenous food, as much milk and beef tea as you please, the tissues still waste; give as much water as you please, the thirst, the dry skin, and the scanty elimination of water continue. The nitrogen and water thus supplied are in great part consumed by the fever poison and do not go to the tissues.
In the muscles such action causes wasting and loss of power; in the heart feebleness; on the skin and mucous surfaces dryness; in the brain the disturbance shows itself by wandering and delirium.
The febrile symptoms of the malarial fevers are to be explained in the same way—their poisons are reproduced in the blood, and con sume the nitrogen and water of their environment; and so long as this action goes on the fever continues.
But the question remains, " Why is the fever intermittent?" Mala rial poisons grow in and at the expense of the system. They are therefore parasites. It is a rule of almost universal application in the parasite world that each parasite has its own special nidus or habitat in which it is reproduced, and away from which it ceases to manifest life and activity. The parasite of ringworm affects the roots of the hair of the head; that of sycosis the roots of the hair of the mus tache and beard; the trichina spiralis makes its nest in muscle rather than in any other tissue; the fluke-worm of sheep makes its home in the liver. In the same way the poison of typhoid fever affects the glands of the small intestine; that of scarlet fever the skin and throat; that of measles the skin and mucous surfaces of the respiratory tract; that of relapsing fever makes a habitat of the blood. Why each of these parasites has its special habitat we do not know; but we know for a fact that it is so, and that each parasite finds in its nidus some thing which is necessary to its vivification and reproduction, as dis tinguished from its organic growth, and which it finds nowhere else. It is the existence of the nidus that leads to the localization of each parasitic disease in a particular locality, and so gives to it one of its distinctive features—a special seat; it is its special local lesion which imparts to each of the specific fevers the distinctive features by which it is recognized. Small-pox is known by its eruption, and it is in the matter of its pustules that the poison most abounds. The dis tinctive feature of typhoid fever is the intestinal lesion; the affected glands are the nidus of the typhoid poison, the special seat of its vivification and reproduction; it is in the discharges which come from them, therefore, that the typhoid poison is most abundant. For the same reason the poison of scarlet fever most abounds in the dis charges from the throat and in the peeling cuticle. The only one of the specific fevers which has no local lesion is relapsing fever, its distinctive feature being the relapse; it is also the only one whose poison is found abundantly in the blood. It is a contagious fever, and therefore its poison ranks with the contagia. But though patho logically ranked with the contagious fevers it has many clinical analo gies with the malarial. It is in fact a sort of clinical link between the two. It ranks with the specific fevers inasmuch as it is contagious, occurs in an epidemic form, and runs a pretty definite course; it resembles the malarial fevers inasmuch as it has no special local lesion, has for its distinctive feature an intermission, a period of apyrexia between two attacks of fever, and inasmuch as one attack confers no immunity from a second.