3io POPULAR SCIENCE MONTHLY. 



MALARIA AND THE MALARIAL PARASITE.* 



By PATRICK M ANSON, M. D., LL. D., 

 LECTURER ON TROPICAL DISEASES AT ST. GEORGE'S HOS "ITAL AND CHA RING-CROSS HOSPITAL 

 MEDICAL SCHOOLS AND AT THE LONDON SCHOOL OF TROPICAL MEDICINE. 



THIS lecture is devoted to a description of the parasite and of its 

 life cycles. The existence of a parasite in malarial disease has 

 been suspected for a long time, but only very recently have we had 

 absolute assurance that such a parasite exists. Some time in the 

 thirties Meckel described in the human blood certain black particles 

 which he found in leucocytes and in certain pale, leucocyte-like bodies 

 the nature of which he did not know. When he saw these bodies he 

 certainly saw the malarial parasite. His observations were repeated 

 and extended in the forties and the fifties by Ererichs and Virchow, 

 and they, too, undoubtedly saw the malarial parasite. But it is one 

 thing to see and quite another to recognize; discovery is recognition. 



The discoveries of Laveran, Clolgi, Marchiafava, Bignami and others 

 resulted in considerable knowledge of the life history of the malarial 

 parasite and of the correspondence between its life cycle and the clini- 

 cal cycle of the disease. Laveran discovered the parasite; Golgi de- 

 scribed the cycle of the tertian and quartan forms; the others added 

 new data, especially concerning the more malignant parasites. The 

 malarial parasite in its mature form has the appearance — I shall take 

 the tertian parasite as a type — of a mass of pale protoplasm occupying 

 practically the whole of the red blood corpuscles. Scattered through 

 this mass of protoplasm are a number of black specks or little rods of 

 intensely black pigment. Later in the life of the parasite a peculiar 

 thing happens: all these little specks of black pigment concentrate 

 usually towards the center of the organism whilst the pale protoplasm 

 arranges itself into little spherules, the whole constituting what is 

 known as the 'rosette body.' Later in the life of the parasite the sur- 

 rounding blood corpuscle breaks away and this rosette body floats free 

 in the liquor sanguinis and then breaks up into its constituent spores, 

 setting free at the same time the black pigment clump. Phagocytes 

 attack many of these free spores and probably absorb most of them, as 

 well as the little pieces of pigment. The result is the pigmented 

 leucocyte, so characteristic of malarial blood. A few of the spores 

 escape and in virtue of some peculiar faculty, which is not at present 



* Abstract of a lecture delivered at the Medical Graduates' College and Polyclinic, and printed 

 in the Lancet of May 19. 



