GUINEA-WORM 



125 



largest of the human filariae, and causes much pain and 

 a great deal of disablement. Where the worm is common 

 a serious loss of labour is the result. 



The effect of the infection of the host is frequently 

 known as Dracontiasis. Rarely the worm, before it is 

 sexually mature, may enter an unusual place, such as 

 the knee-joint, and cause serious trouble. In the ordinary 

 course of events when mature it approaches the skin, so 

 that the head is immediately below the cuticle. This 



FIG. 59. On the one foot is to be seen the large blister formed when the 

 Guinea-worm is mature ; on the other a blister has burst, a raw surface is 

 exposed, and the head of the Guinea-worm may be seen protruding. 



takes place some eleven to twelve months after infection. 

 When quite mature probably an irritating fluid is dis- 

 charged by the worm in the subcutaneous tissues. A 

 blister then forms, often an inch in diameter (fig. 59). This 

 blister bursts in a day or two, and the head of the worm 

 may be seen at the bottom of a small pit in the raw 

 surface left. If the part is placed in cold water, or water 

 dashed on the skin close to the blister, the head of the 

 worm will be protruded further through the opening. 

 If the head be carefully watched it will be seen that a 

 bladder-like protuberance forms from time to time in 

 front, bursts, and discharges a milky fluid. At one time 



