FILARIAL WORMS 317 



As regards the life history, Fedschenko, in 1870, showed that the embryos when 

 liberated swam around in water and finally entered the bodies of species of the genus 

 Cyclops. The female tends to come to the surface in the lower extremities, and 

 experiments show that if on the blister-like points of emergence some water be 

 squeezed out from a sponge, the uterus will eject a milky-looking fluid containing 

 myriads of embryos. This would indicate that the worm selects the lower extremity 

 so that the embryos may gain access to the Cyclops when the host is wading through 

 the water. 



Leiper showed that a strength of HC1 equal to that of gastric juice killed the 

 Cyclops, but made the Dracunculus embryos very active. From this he judged that 

 infection must probably take place from drinking water containing infected Cyclops. 

 The suggestion of Leiper that wells harboring Cyclops be treated with steam, intro- 

 duced by a pipe, seems to be valuable. The disease is known as "Dracontiasis." 



Filaria loa (Filaria oculi). This is a thread-like worm of west 

 Africa about i to 2 inches long. The cuticle is characterized by 

 distinct wart-like structures. 



The anterior extremity is like a truncated cone with two papillae at the base of 

 the cone. The wart-like cuticular protuberances or bosses are about 12 to 15 

 microns in height. The females are 2 to 3 inches (50 to 70 mm.) long and about % 

 mm. broad. 



The males are smaller than the females and have three preanal papillae and two 

 postanal ones. There are two short unequal spicules. The life history is not satis- 

 factorily established. The young are born ovoviviparously, and it has been sug- 

 gested that the localized cedemas, known as Calabar swelling, may be due to the 

 irritation produced by these eggs. These swellings are of hen's egg size, painless, 

 do not pit on pressure and last about three days. They occur especially on the hands 

 and arms. The embryos almost exactly resemble those of F. bancrofti. They have 

 a diurnal periodicity, however, appearing in the blood about 8 A. M., increasing to 

 noon and disappearing about 9 p. M. The adult worms have a tendency to wander 

 about in the subcutaneous connective tissue, especially about the region of the orbit 

 or even under the conjunctiva. 



Adult worms of F. loa have been found and extracted, with an absence of the 

 filarial embryos in the peripheral circulation of the patient. While immature adult 

 worms have been extracted from children the embryos have only exceptionally been 

 found in these children. This would speak for a very long developmental period 

 for the adult worm and as a matter of fact the infection often only shows itself years 

 after the opportunity for infection. 



Leiper has just noted two species of Chrysops (Mangrove Flies) as intermediate 

 hosts, the embryos developing in the salivary glands. 



Filaria bancrofti (Filaria sanguinis hominis). This is the most 

 important of the filarial worms. It is a common infection in south 

 China, India, the West Indies, and in the Pacific Islands, especially 

 Samoa. 



