The brain has a leaden hue caused by the black pigment. As discussed under pernicious manifestations the blocking of the capillaries may be explained in several ways. When examining sections of a malarial brain one often encounters punctiform haemorrhages.
The spleen is enlarged and the surface dark. In acute cases it may be diffluent instead of hard, as in ague cake. Microscopic sections show a striking absence of pigment in the Malpighian corpuscles, the haemozoin being pushed off into the surrounding spleen pulp. Bone marrow is dark from deposit of pigment. In the liver the endothelial and Kupfer cells are packed with black pigment. The parenchymatous cells do not contain this pigment but may show grains of a yellow pigment, haemosiderin, which gives the iron reaction. Haemozoin, although it contains iron, does not give this reaction. Haemozoin is soluble in alkalis, but not in alcohol while haemosiderin is soluble in alcohol but not in alkalis.
The splenic blood is more rich in haemozoin than that of the other vessels, this indicating the spleen as the place of destruction of infected red cells or as the nursery for the development of malarial parasites. As a matter of fact splenectomy may cure an old malarial cachectic.
The finding of pigmented mononuclears or pigmented parasites in a cross section of a blood vessel makes for a diagnosis of a malarial infection.
Malarial manifestations are common in tropical autopsies and one must be very chary about reporting malaria as the real rather than contributing cause of death.
There is usually a marked increase in large mononuclears in malaria and if this is noted along with a leucopenia it is very suggestive. Melaniferous leucocytes occur in malaria only.
The kidneys may show degenerative changes and the presence of urobilin in the urine is an important indication of latent malaria.
Symptomatology
Clinically, we have two types of malarial paroxysms, (1) Those presenting a cold stage, followed by a hot stage, with a terminal sweating stage. Such attacks are brought about by the benign infections which include the benign tertian and the quartan. Owing to the fact that in such paroxysms the temperature makes a critical fall to normal or subnormal readings such fevers are frequently designated intermittent fevers.