Æstivo-autumnal parasites, including the crescentic bodies, are always extracellular; that is, they are attached to the external surface of the red corpuscles.
Crescentic bodies attach themselves to the red corpuscles just as the younger parasites do, by encircling, with their cytoplasm, mounds of hemoglobin substance. These hemoglobin mounds may be seen protruding through various portions of the crescentic bodies, as well as at the periphery of the parasites. The base of the mounds is occasionally outlined by the chromatin or pigment granules.
The hemoglobin mounds protruding through the body proper of the crescentic bodies do not seem to alter the general outline of the parasites. The outline of the parasites may be traced through the transparent mounds.
Whenever attaching pseudopodia are observed they are seen to arise from the cytoplasm of the parasites and may be in the form of loops or strings.
When the crescents are attached they proceed to dissolve the hemoglobin to make it available for utilization, assimilating what is required for nutrition, the waste product being in the form of pigment granules.
After the hemoglobin mounds, to which the crescents are attached, have been decolorized by parasitic action, an appearance is obtained which has been described by most observers as vacuolization of the crescentic body. These observers believe the picture to be one of degeneration.
The decolorized mounds or vacuoles ("achromatic areas") seen in connection with malarial parasites correspond to the nutrition vacuoles of the common amebæ, and possibly the malarial parasite may, like these amebæ, secrete reserve food.