294 THE ANIMAL PARASITES OF MAN 



a new species and retained the name of F. ozzardi suggested by 

 Manson. Adult forms of the African blunt- tailed larvae were next 

 found by Mr. O'Neil at the necroscopy of a Congolese patient 

 who died from sleeping sickness in Charing Cross Hospital, and 

 Manson, after a comparison between these and the British Guiana 

 specimens, came to the conclusion that they were identical. 



The larval Filaria perstans measures on an average O'2 mm. in 

 length by 0*0045 mm. in breadth ; it has a blunt, truncated tail, 

 and possesses no sheath. The head is provided with a retractile 

 fang. The anterior gap in the central column of cells (Manson's 

 V spot) is at about 0*03 mm. from the cephalic extremity. 

 There is no marked tail gap. Having no sheath, these larvae are 

 able to move rapidly and freely all over the slide. The larvae 

 of F. perstans observe no periodicity. Their numbers in the 

 peripheral circulation may vary considerably, but there is no 

 marked difference between day and night. Their special seat of 

 selection is not the peripheral blood, but that of the heart, lungs, 

 aorta and other large vessels. They are never found in the 

 spleen, and only rarely in the liver and pancreas. 



The adult female F. perstans measures 70 to 80 mm. in 

 length by O'i2 mm. in breadth. The head is club-shaped and 

 measures 0*07 mm. in diameter. The genital pore opens at o - 6 

 mm. from the head. The tail is curved and presents a cuticular 

 thickening, which forms two tiiangular appendages. The anus 

 opens at the apex of a papilla situated in the concavity of the 

 curve formed by the tail. The diameter of the tail just before 

 termination is 0*02 mm. 



The adult male measures 45 mm. in length by cro6 mm. in 

 breadth. The diameter of the head is 0-04 mm. Close to the 

 opening of the cloaca there are four pairs of pre-anal papillae 

 and one pair of post-anal papillae. Two unequal spicules may 

 sometimes be seen protruding from the orifice. 



The adult worms inhabit the connective tissue at the base of 

 the mesentery. To find them the mesentery should be removed, 

 placed in a 2 per cent, solution of formalin, and then carefully 

 examined at leisure. 



Filaria perstans has a wide geographical distribution. In 

 Africa it is very common in certain districts along the west 

 coast. Drs. Annett, Button and Elliott report its presence at 

 Sierra Leone, on the Kroo Coast, on the Ivory Coast, on the 

 Gold Coast, at Lagos, in Northern and Southern Nigeria ; Manson 

 found it in slides of blood from Old Calabar and from the Congo. 



