prodigious number of parasites present in some malignant infections. As development advances, the invaded corpuscles seem to be filtered out by the capillaries and small arteries (Plate II., Fig. 2, A, B, c) of the deeper viscera and of the bone marrow. So that even in severe infections the later pigmented stages are by no means proportionately represented by, or even frequently encountered in, finger blood; the segmenting form (Plate I., Fig. 3, i, j) still less so. To find numerous examples of the more advanced stages of these parasites it is necessary to aspirate splenic blood, or to search in fatal cases in the deeper viscera, or in the bone marrow immediately after death. Owing to this absence of the more advanced forms from the peripheral circulation, the duration of the life span of these parasites is difficult to fix; probably it varies between twenty-four and forty-eight hours, being not very constant even in the same type.
"Brassy bodies."—— Malignant parasites frequently lead to a shrivelling of the invaded corpuscles, many of which, in consequence, are small, crenated, or folded, and very dark. This corpuscle the Italians, from its colour, have designated "brassy body" (Plate I., Fig. 3, e). In the interior of these corpuscles the parasite can generally be made out as a minute pale ring.
The crescent-foody characteristic.—— Most distinctive feature of all, the malignant parasites—— at all events the subtertian—— form crescent gametocytes.
Time when crescents appear; not a fever form.—— It has been already remarked that these crescent bodies are not to be seen at the very commencement of an infection. A week usually elapses between the first appearance in the peripheral blood of the small intracorpuscular parasites and the first appearance of the crescent bodies.*[1] Once the latter begin to appear,
- ↑ * There has been a good deal of speculation as to why certain parasites develop into schizonts, whilst others become gametocytes. The circumstance of the late appearance of the gamete is looked upon by some as evidence that the blood, from repeated development in it of swarms of endogenous parasites, has become exhausted as a pabulum, and that in consequence of this the parasite is directed to a line of development providing for life and growth elsewhere, that is in the mosquito. The analogy of other sporozoa and of the bacteria supports this view.
