298 DISEASES DUE TO HELMINTHS 



The anus is 80 i-i from the tip of the tail. There are three pairs of 

 pre-anal and two pairs of post-anal papillse. 



The worm carries two spicules of unequal length ; the larger is 

 traversed by a fine canal (Penel). There are rounded bosses scattered 

 over the cuticle averaging 30 yu, in height. 



The mouth is terminal, small, unarmed, with a powerful muscular 

 cone. 



The oesophagus is short and is not bulbous. 



The excretory pore is 0*65 mm. from the anterior end. 



The worm has a tubular testis and vas deferens filled with spherical 

 spermatozoa, which organ terminates in a vesicula seminalis near to 

 the base of the spicules. 



The female is 44 to 63 mm. long by 0*4 mm. thick. The vulva is 

 2*5 mm. from the anterior end. 



LIFE-HISTORY. 



The unsegmented egg is 32 by 17 /x | 



The morula stage is 40 by 25 /x. In uterus. 



The rolled-up embryo is 50 by 25 /x.) 



The embryo approaches the vulva, unrolls and elongates itself 

 inside the egg membrane before it is extruded ; the embryo then 

 measures 250 by 6 /x The embryo now escapes into the lymph 

 stream and blood current, where it is known as Microfilaria diurna. 

 In the circulation it enlarges to 298 by 7*5 /x, perhaps by osmosis. 

 The microfilarias do not completely fill their shealh. 



HABITS. 



They are seen in the peripheral blood during the day, but not at 

 night. They have no relation to sleep as the Microfilaria bancrofti. 

 The curves are irregular; in the Mf. bancrofti they are graceful. The 

 microfilarias when found in the peripheral blood are never in such 

 numbers as the Mf. bancrofti. 



The Mf. diurna requires from three to four years in the human 

 body before it reaches maturity; they then live for fifteen years or 

 more. 



The immature forms are usually found in children, but the mature 

 forms in adults. 



The rate of progress in the human body is supposed to be one inch 

 in two minutes. Warmth such as that from a fire or the direct sun 

 will attract them to the surface. 



The worm becomes cretified when dead. 



CARRIER. 



This is the Chrysops dimidiata and silacea (Leiper). 



It is one of the Tabanidse with hind tibias armed with spurs. 



