The patient feels more prostrated and ill than does one in a benign paroxysm and there is a distinct tendency to mental confusion or delirium. Nausea and vomiting may be prominent features of an attack. At times an apathetic state may suggest typhoid fever. In these malignant malarial attacks the spleen is palpable and very tender. There is also a sense of weight in the region of the liver. In a blood examination one is not apt to find any other parasites than the young hair-like ring forms which begin to appear a few hours after the onset of the paroxysm. The rings may be observed to broaden, but prior to that development in which pigment would appear in the ring, the parasite-containing red cell is caught in the capillaries of spleen or other organs. The finding of young ring forms while fever continues is suggestive of a malignant tertian infection. In the absence of quinine administration the finding of parasites is to be expected in benign tertian and quartan infections, but with the tropical parasite a smear may fail to show any organisms where a few hours previously a blood examination would have shown a large percentage of infected red cells in every field of the microscope. =Pernicious Manifestations of Malaria.=—These grave manifestations arise almost exclusively in the course of malignant tertian infections. In his study of malaria Stott had about 1% of his cases showing well-marked pernicious symptoms. [Illustration: FIG. 19.—Temperature chart of malignant tertian fever showing how readily one might confuse such a chart with that of typhoid fever. (From Jackson’s Tropical Medicine.)] As explanations of perniciousness are given: (1) the very large number of red cells infected and destroyed by the malarial parasites; (2) the throwing off at the time of sporulation of the merocyte of a large amount of toxic material owing to the presence of such a large number of disintegrating merocytes, and (3) from the plugging of the capillaries of important internal organs by adult parasites. This may arise as the result of (_a_) the sporulating parasites acting as emboli, being too large to pass the lumen of the capillary; (_b_) from degenerative changes or distension with pigment of the endothelial cells lining the capillaries, or (_c_) as the result of an ovoid shape on the part of the malignant tertian parasite there is an inability to pass through capillaries which the flattened benign parasites can do by infolding (Bass), or (_d_) resulting from the tendency of malignant tertian parasites to agglutinate. _Types of Pernicious Malaria._—It is customary to divide pernicious malaria into the following divisions—(1) Cerebral, (2) Algid, (3) Bilious Remittent and, possibly, also (4) Pneumonic and (5) Cardiac types. Blackwater fever is often included in the grouping but would appear to be best considered as a separate disease although almost surely brought about by malaria.