Page:Popular Science Monthly Volume 58.djvu/374

366 that they are not directly concerned in the production of the phenomena which constitute a malarial attack and that the administration of quinine has no influence in causing them to disappear from the blood. On the other hand, the febrile phenomena are directly associated with the appearance of the amœboid form of the parasite in the interior of the red blood corpuscles and the administration of suitable doses of quinine has a marked effect in causing these amœba-like micro-organisms to disappear from the blood.

These crescentic bodies are not found in the benign tertian and quartan intermittent fevers, but are characteristic of the malignant forms of malarial infection, including the so-called æstivo-autumnal fever. In these forms of fever they are not seen at the outset of the attack, and they have no direct influence upon the course of the fever. A week usually elapses between the first appearance of the amœboid form of the parasite and that of these crescentic bodies. They are often found in the blood some time after all symptoms of fever have disappeared, and are associated with the malarial cachexia which follows an attack of æstivo-autumnal fever. When blood containing these crescents is ingested by a mosquito of the genus Anopheles the following very remarkable transformations occur: Some of the crescents are transformed into hyaline flagellate bodies having active movements; others are changed into granular spheres. The flagella break away from the hyaline bodies and, approaching the granular spheres, appear to seek energetically to enter these bodies. A minute papilla is given off from the surface of the sphere, seeming to be projected to meet the attacking flagellum. At this point, one of the flagella succeeds in entering the sphere, causing an active movement of its contents for a brief time, after which the flagella disappear from view, and the contents become quiescent. This is no doubt an act of impregnation. After a time the impregnated granular sphere alters its shape, becoming oval, and later vermicular in form. The pigment granules are now seen at the posterior part of this body, which, after the changes mentioned, exhibits active movements. It is believed that this motile vermicular body penetrates the wall of the mosquito's stomach. Here it grows rapidly and, after a few days, may be seen projecting from the surface as a spherical mass. In the meantime the contents are transformed into spindle-shaped bodies (sporozoites) which are subsequently set free by the rupture of the capsule of the mother cell. According to Manson, these spindle-shaped bodies pass from the body cavity of the mosquito, probably by way of the blood, to the three-lobed veneno-salivary glands, lying on each side of the fore part of the thorax of the insect. "These glands communicate with the base of the mosquito's proboscis by means of a long duct along the radicles of which the clear, plump cells of the gland are arranged. The sporozoites can be readily recognized in many, though not in all, of the