THE BIOLOGICAL CONTROL OF LIFE 37 



few years ago quite a number of religious and worthy 

 Boer farmers — unconsciously impious — refused to join 

 in with the Anti-locust league, giving for their reason 

 that it was attempting to stay the hand of God. So 

 did some religious people in Scotland protest against the 

 use of chloroform in childbirth. 



The definitely modern phase may be illustrated with 

 reference to the checking of malaria. This disease, 

 whose name, meaning bad air, takes us back to the days 

 before it was understood, is due to a microscopic animal 

 {Plasmodium) which was demonstrated by Laveran 

 (1880) in the red blood corpuscles. The parasite forms 

 spores in the corpuscles, and these spores are set free 

 in the blood, their behaviour corresponding to the 

 patient's chills and fevers. In 1894 Grassi showed that 

 part of the life of the malaria parasite is spent within 

 the mosquito, and the details of the story are com- 

 plicated. By their bites the mosquitos become infected 

 and by their bites they also infect. In 1898 Ross proved 

 that fogs and vapours and marshes are merely of indirect 

 moment in producing the disease, which can only be 

 acquired if an infected mosquito introduces some of 

 the parasites into man. If man can protect himself, 

 with mosquito-curtains or the like, from mosquito- 

 bites, he protects himself ifso facto from malaria. 

 Moreover, the larval mosquitos live in water-pools, and 

 have to come to the surface to breathe. If a Little petrol 

 be poured on the pool, it forms a surface-film to 

 which the breathing-tube of the larval mosquito cannot 

 adhere. Thus the young mosquitos are suffocated 



