I20 INFECTIOUS AND PARASITIC DISEASES. 



Filarial embryos are looked for in fresh blood- 

 specimens the same as for malaria. There is a peculiar 

 periodicity about their appearance in the peripheral cir- 

 culation in the respect that they are found only at night. 



Mosquitoes (culex) act as intermediate hosts for 

 these filaria, abstracting the embryos from one person 

 and inoculating them into others. Persons suffering 

 from filariasis are therefore not only a danger to them- 

 selves (on account of repeated inoculations) but to 

 others who may chance to be bitten by infested mos- 

 quitoes. In man again, the embryos mature, reach a 

 lymph vessel and there begin producing fresh embryos. 



Hcematochyluria is also caused by the -filaria san- 

 guinis hominis. However, both this and elephantiasis 

 may be due to other causes. 



Besides the above filaria, two others are recognized 

 by Manson, the Filaria diurna, the embryos of which 

 are found in the peripheral circulation during the day- 

 time only, and of which Manson suspects the Filaria loa 

 to represent the adult worm, and the Filaria per s tans, 

 which the same author regards as the cause of a skin 

 eruption, craw-craw, found on the west coast of Africa. 

 A round worm of whitish or yellowish 

 Filaria Loa. color, from 20 to 40 millimeters (i and 2 

 inches) in length by 3 to 5 millimeters in 

 breadth, and found in the subcutaneous tissues, usually 

 of the face, but more especially in the conjunctivae. 

 Its movements in the skin, which are visible to the eye, 



