42 KEY FOR DIAGNOSIS OF HUMAN HELMINTHS 



itching and the finding of mature females and eggs in the 

 stools. The following key is included to aid in the diagnosis 

 of the diseases produced by parasitic worms. 



3. KEY FOR DIAGNOSIS OF HUMAN HELMINTHS 



A. Larvae, microfilariae, in blood (the part of the key on the micro- 



filariae is adapted from Stitt). 

 1. Sheath present. 



a. No periodicity. 



Filaria philippinensis. Tightly fitting sheath, not 

 flattened out beyond extremities; tail pointed and 

 abruptly attenuated; 290ju to 320/i by 5ju. 



b. Periodicity. 



1. Noctural periodicity. 



Filaria bancrofti (Plate VI, Fig. 3). Tail 

 pointed; sheath loose; V-spot 90/i from head; 

 break in cells 5(V from head; 300/x by 7.5/i. 



2. Diurnal periodicity. 



Loa loa (Filaria loo) (Plate VI, Fig. 2). Tail 

 pointed; sheath loose; V-spot GO/* to 70/z from 

 head; break in cells 40/x from head; 245/x by 7/i. 

 II. Sheath absent; no periodicity. 



a. Tail blunt 



Acanthocheilonema perstana (Filaria perstans) (Plate 

 VI, Fig. 4). 190/i to 200^ by 4.5/x to 5/x. 



b. Tail sharply pointed. 



1. 200 M by 5/t. 



Filaria ozzardi (F. demarquayi) . (Plate VI, 

 Fig, 1). 



2. 250/i to 300/* by 5/x to 7/*. 



Onchocerca volvulus. Microfilariae of this species 

 have not been seen in blood but only in lymph 

 spaces around females. 



B. Larvae in feces, rhabditiform state. 



I. Length of buccal cavity only one-half the diameter of 



body. 



Strorigyloides stercoralis (Plate VI, Fig. 8). 200/* to 250/i 

 by 13/i to 15/z; genital anlage about 30/* in length. 



