PATHOLOGY 



1145 



all over the body, and should be found equally distributed, no matter 

 what organ is examined. This would be so if the parasite did not 

 seriously damage the red cell, and, by its toxins, the endothelium 

 of the vessels, especially that of the capillaries, in which the blood- 

 flow is slowest. It would appear as though the damage done to 

 the red cell by the quartan parasites is not severe enough to cause 

 them to be caught in the capillaries. Therefore the whole life- 

 history of the quartan is spent in the circulation, and sporulating 

 forms can be readily seen in finger-blood. 



Tertian parasites, on the other hand, seriously affect the red cells, 

 causing swelling, degeneration, and decolor iz at ion. The tropho- 

 zoite and schizont stages are easily seen in the peripheral circulation. 

 Still, the sporulating forms are more common in the spleen, which 

 may be looked upon as having filtered them off from the blood 

 which passes through it. 



The subtertian parasites act deleteriously on the corpuscles, 

 making them smaller and darker. They rarely appear in the peri 

 pheral circulation in the sporulating condition, while they abound 

 in the spleen and internal organs. On examining the organs post 

 mortem, it will be found that the schizont and sporulating forms 

 are found in the capillaries, while the trophozoites are found attached 

 to the walls of the arterioles and venules. 



The sporulating parasites give rise to h^emozoin, which escapes 

 from the corpuscle along with the merozoites, and will therefore be 

 most commonly found in those tissues and organs in which sporula- 

 tion takes place — e.g., spleen, liver, and bone-marrow — and will give 

 them a definite coloration, varying from a reddish-brown to a 

 black, according to the quantity present. 



This pigment will, of course, be also met with in the peripheral 

 blood, both free and inside mononuclear leucocytes, for, on escaping 

 from the parasite, the haemozoin is seized by the mononuclear 

 leucocytes, macrophages, and the endothelial cells of capillaries; 

 therefore, in acute malaria, it will be distributed evenly through the 

 organ affected. The pigment is later conveyed from the blood- 

 vessels into the tissues by the phagocytes, and is found in the con- 

 nective tissue of the organ close to the bloodvessels. Eventually it 

 disappears, being partially digested by the phagocytes and tissue 

 cells and partially removed by the lymph. This process, however, 

 cannot continue without causing irritation of the connective tissue. 



Not merely does pigment escape from the sporulating parasite, 

 but also haemolysin, which damages the red cells, and causes the 

 appearance of another pigment, yellowish in colour, called ' haemo- 

 siderin.' This is deposited in the parenchyma cells of the organs — 

 e.g., the liver — and may perhaps damage them. The presence of 

 this haemolysin has been confirmed by the researches of Simpson. 



Another toxin — this time pyrogenous — also escapes from the 

 sporulating parasite, and may be the cause of the hyperaemia found 

 in the internal organs — e.g., the spleen and the liver in acute malaria 

 — and may also cause the destruction of the parenchyma cells of 



