Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER HI PATHOLOGIC ANATOMY OF MALARIA ACUTE MALARIA Intravascular melanin, which is a product of hemoglobin converted through the biologic agency of the malarial parasites, is the pathognomonic anatomic feature of malaria. Melanin occurs in the tissues also, but here there is some doubt as to its origin. It is brownish black in color, occurs in fine grains, coarse particles, or in lumps; does not yield the reaction for iron, and is insoluble in acids, but is readily dissolved by ammonium sulphide. This should not be confused with hemo- siderin, which is a chemic derivation of the hemoglobin of broken-down red blood-cells; is yellowish in color; responds to the reaction for iron; is insoluble in acids, alkalies, alcohol and water; and exists especially extravascularly. It is regarded as a result of prolonged hemoglobinemia following severe or chronic infections. The general plan of distribution of melanin may be thus stated: In the blood current it may exist free or, more commonly, is contained within the phagocytes and the red cells infected with pigmented parasites, and is more abundant in the capillaries than in the larger vessels. In the viscera it is oftenest seen in the spleen, bone-marrow, brain, and liver, especially in the endothelial cells, but in the spleen and bone-marrow it exists also outside the vessels and either between or within the cells proper to these tissues. The distribution of the parasites varies according to the type of the attack; it has been shown that the latter depends largely upon the localizations of the parasites. They are usually abundant in the splenic blood irrespective of the form assumed by the attack. It occasionally happens that death supervenes, notwithstanding a progressive diminution of the parasites, so that the latter may...