THE RECOIL OF MAN'S INFLUENCE 511 



surface, and stagnate in the hollows, which are here to be found in every 

 field. 



To these stagnant pools he attributed the " remote cause of 

 intermittent fevers." Even more interesting is the statement 

 of the incumbent of Kirkbean parish in the same county of 

 Kirkcudbright : 



Formerly many of the inhabitants went into Lincolnshire [an area long 

 noted for the prevalence of ague] for employment during the harvest, and 

 returned infected with this disease, now they have work sufficient to 

 employ them in the parish and the disease is seldom a complaint. 



In recent years science has thrown a new light on the 

 cause of ague, intermittent fever, or malaria, as it is variously 

 termed. The malady is due to the presence of minute para- 

 sites of low organization in the human blood. At one stage of 

 their existence these haemamcebse (Plasmodium) attack and 

 bore their way into the red blood-corpuscles, in which they 

 undergo a process of multiplication until at last the blood- 

 cells break down and the multitudes of freshly formed 

 parasites are set free in the blood stream. It is at this 

 stage of the disruption of the blood-cell, that the patient has 

 a relapse of fever, the interval between relapses about 

 forty-eight hours in tertian ague, seventy-two in quartan 

 ague, and an uncertain interval in the irregular fever de- 

 pending directly on the length of the life-cycle of the parasite. 



No\v an interesting and vital connection exists between 

 the tiny Plasmodium parasite of the human blood and the 

 insect world, for the virulence of the parasite in man dwindles 

 if it does not undergo a periodic reincarnation within the 

 body of a Mosquito. The Mosquito becomes infected by 

 stealing a drop of the parasitized blood from a malarial 

 patient, and it passes on .the parasites and the infection when 

 it punctures the skin of a healthy subject. The Mosquito 

 therefore is essential to the spread of malaria or ague amongst 

 men. 



The habits of Mosquitoes, and by such I mean Anopheline, 

 or, as a rule, "spot-winged" Gnats, are familiar to every 

 naturalist. They like moist, warm, humid places, and the)' 

 most often frequent marshy and boggy ground, sluggish 

 streams, and stagnant pools, large or small. On the surface 

 of the water, often along the weedy margins of pool or 

 ditch, the eggs are laid and the wriggling larvae and 



