134 MALARIA 



Ireland, which appears at first sight peculiarly 

 adapted for the disease, seems to have been remark- 

 ably free from it. It may be that the strong anti- 

 septic quality of the peaty bog -water hinders the 

 development of the larval mosquito. 



Turning now to the cause of the disease, it is 

 interesting to note that the discovery of the organism 

 which produces all this misery and death took place 

 just about the time when Koch was making his far- 

 reaching investigations into the cause of tuberculosis. 

 In 1880 Koch was at work on the tubercle bacillus; 

 and in the same year a French army surgeon, named 

 Laveran, looking down a microscope in a remote 

 military station in Algiers at a preparation of blood 

 taken from a malarious soldier, recognized for the 

 first time the small organism which has played a 

 larger part in human affairs than the greatest politician 

 or general that ever lived. This small organism is 

 an animal, not a plant. It belongs to the great group 

 of single-celled organisms, mostly microscopic in size, 

 called Protozoa, and it lives as a parasite inside the 

 body of other animals, from which it abstracts what 

 nutriment it needs. Before describing its structure 

 and life-history, a word or two must be said about its 

 surroundings in the body of man. 



That blood consists of a fluid in which enormous 

 numbers of cells called blood-corpuscles float is now 

 a matter of common knowledge. These corpuscles are 

 of two main kinds, the red and the white, but the red 

 surpass the white in number, in proportions ranging 

 from 300 up to 700 to i. A cubic millimetre of blood 

 contains about 5,000,000 red corpuscles; and since 

 these act as the carriers of oxygen from the lungs to 

 the tissues all over the body, and on their return 

 journey carry away the carbon dioxide from the 

 tissues to the lungs, where it is given off, it is obvious 

 that the presence of a parasite in the red corpuscle 



