MICROFILARIAE 319 



the peripheral circulation hence perstans. There does not seem to be any symp- 

 tomatology. 



It is of historical interest that F. perstans was once considered the cause of sleeping 

 sickness. 



Onchocerca volvulus (Filaria volvulus). This is a rather common parasite of 

 central Africa. The male is about i% inches (35 mm.) and the female about 5 inches 

 long. The females are so interlaced in the fibro-cystic swellings that it is difficult to 

 determine their length. The tumors start from the presence of a worm in a lym- 

 phatic. The tumors are easily enucleated. Adults are striated. They are found in 

 cystic tumors, especially about the axilla and popliteal space. The cystic contents 

 contain abundant sheathless larvae about 300/1 long. It was formerly thought that 

 these larvae were absent from the peripheral circulation but more recent investiga- 

 tions have shown a sheathless embryo in the blood of patients with Onchocerea 

 nodules which had the characteristics of those found in the contents of the nodules. 

 Life history unknown, although it has been suggested that a species of Glossina may 

 be concerned. 



Filaria demarquayi. The habitat of this filarial worm is the West 

 Indies. The embryo has no sheath and has a sharp tail. Other filarial 

 species which have been reported are F. magalhcesi, F. ozzardi, F. 

 volvulus, F. powellij and F. philippinensis. A species called F. gigas 

 is now considered to have been only the hair of the leg of a fly. The 

 embryos have usually been given such names as F. nocturna, F. diurna, 

 etc. Of course the embryos and the parent should have the same name. 

 It has been proposed to designate these embryos the same as the parent, 

 but with the use of the term Microfilaria instead of Filaria. 



The points usually noted in the description of filarial embryos are: 



1. Presence or absence 6f periodicity of embryos in peripheral 

 circulation. 



2. Presence or absence of a sac sheath around the embryo. 



3. Accurate measurements. 



4. Shape and description of head and tail ends. 



5. Character of movement. 



6. Location of V spot and break in cell column in stained 

 specimens. 



KEY TO FILARIAL LARV.E IN PERIPHERAL CIRCULATION 



A . Sheath present. 



1. No periodicity. 



F. philippinensis. Tightly fitting sheath; not flattened out beyond extremi- 

 ties. Tail is pointed and abruptly attenuated. Lashing progression move- 

 ment. 320 X 6.5;*. 



2. Periodicity exhibited. 



