10 Philippine Journal of Science 1920 
the vomiting or passage of worms by the patients during their 
stay in the ward. 
Several factors, some of them rather remote to be sure, may 
intervene to defeat a laboratory diagnosis in certain cases of 
nematode infection. The parasites may be present in exceed- 
ingly small numbers; but in such cases, unless one or more of 
the other conditions to be mentioned is present, the infection 
is almost certain to be detected sooner or later, especially if con- 
centration methods are employed. The worms may be too im- 
mature to produce eggs. In such an event a wait of three or 
four weeks at the most, in a suspicious case, will probably 
settle the matter. Such cases would hardly be likely to develop 
symptoms, however. All the worms present may be males— 
a remote pdéssibility, but one that has been shown by Hall (25) 
to exist in lower animals. Added to these is the difficulty ex- 
perienced in handling dysenteric stools, especially those contain- 
ing considerable mucus; but we believe it is possible, in the 
greater number of such instances, to pick up helminthal infec- 
tions during the course of a series of examinations such as 
we have conducted. We failed to detect the ova of helminths. 
in six individuals among the twenty-two cases of ileocolitis 
that occurred in our series. Of these six negative cases, four 
were found in the group of children between the ages of 1 
and 2 years, eight cases of ileocolitis having occurred in that 
group. This group has been shown to have yielded 26 per 
cent less infections than the other higher groups and about 
7 per cent more than the 7 to 12 months group. However, 
it must be admitted that stools of that character are trouble- 
some and uncertain to deal with, but as we were taking the 
general run of cases, we had to deal with conditions as we 
found them. Incidentally, we might remark that we were un- 
able to determine any marked tendency to expel worms during 
the course of a febrile disorder. It did occur in some instances, 
but it was not an invariable event. 
For some reason or other the ova of Ascaris and Trichuris 
occasionally failed to come down on centrifugation. This oc- 
curred ten times in the case of Ascaris and five times in the case 
of Trichuris. The infections, however, were either detected 
on the slides or were thrown down in subsequent—or, in some 
cases, earlier—concentrations. One very odd situation was 
afforded by a case that was persistently negative for Trichuris 
on concentration and on examination of fresh cover-glass 
