— 335 — 
lis, either filariform embryos, or the sexually differentiated adult 
free-living génération would be detected if présent. Sometimes 
adult Oxyuris vermicularis and hookworn larvae could be se en in 
the Pétri dish culture as well. Some familiarity with the charac- 
teristic appearance and movements of the filariform larvae of 
S. stercoralis is necessary to prevent their confusion with hook- 
worm embryos. Hookworm larvae are at first very sluggish. La- 
ter they bècome more active as they increase in size. At the end 
of 24 hours in a culture of foeces one finds if S. stercoralis is 
présent, either the sexually differentiated adults or filariform lar¬ 
vae (direct phase) or both. The former are easily recognized by 
their size and location near the foecal mass, while the filariform 
larvae are always seen moving actively along the outer margin jf 
the fluid, and having a boring movement as though trying to 
escape through the outer margin of the fluid. They can be segre- 
gated too in the clish by sunlinght or artificial light and heat 
(electric light bulb). Hookworm larvae on the other hand are al- 
w'ays sluggish at this time and they do not seek the periphery of 
the culture. 
Next, a portion of the foeces, diluted with stérile tap water, if 
necessary, was placed on a slide and covered with a cover slip. 
This was examined for protozoa, ova or larvae of Strongyloides. 
The method was used chiefly for the détection of amoebae and 
flagellâtes and in a number of instances for comparison with the 
other methods. 
Finally, the tubes containing the foeces were nearly filled witn 
stérile tap water thoroughly mixed with a glass rod and centrifu- 
ged at 1800 to 2000 révolutions for a few seconds, the superna- 
tant fluid removed and the tubes refilled with a solution of cal¬ 
cium chloride of a spécifie gravity of 1.250, thoroughlv mixed 
and oentrifuged as before. The surface film was now pipetted off 
and examined microscopically on a slide for ova. The upper 
layers in the tubes and the supernatant fluid near the surface Avas 
also examined grossly for adult or immature worms (Pin worms 
and hookworms). This method, after the one used by Bass (i), 
segregates ail the ova, worms and some of the Strongyloides lar¬ 
vae, chiefly the dead ones. By a combination of the methods it is 
possible to increase the number of positive findings very conside- 
rably, as will be seen by reference to the table below. 
(1) B.ass, (C. C.), Archives of Internai MecLicine, 1909, V. III, p. 446. 
