16,1 Haughwout and Horrilleno: Intestinal Parasites 3 
among children under 15 years of age. He has been able to recall 
only a very few cases in an experience extending over nearly 
thirty years. The senior author, in several years’ observation, 
has seen only one case of infection with Balantidium in a young 
child. The child was under treatment for bacillary dysentery 
at the time the ciliates were discovered in its feces; and, al- 
though the case has since been observed from time to time, no 
further dysenteric symptoms have been noted. 
Obligatory tissue parasites, such as Entameba histolytica and 
Balantidium, when they give rise to trouble, usually produce 
symptoms of a fairly positive character; not so with the para- 
sites we have found in this series. We feel we cannot go 
beyond the statement that the association of Ascaris and Tri- 
churis seems to evoke a more or less constant symptom-complex 
which, however, is subject to confirmation by the microscopist. 
The physician is forced to lean heavily on the microscopist for 
diagnosis of these cases, simple as they seem, for we have a 
record of more than one patient in this series to whom santonin 
had been given for ascarids that were not present in the intes- 
tinal tract. In only two instances have we failed to detect the 
ova of Ascaris in the feces of cases that later were shown to 
be infected through vomiting or defecation of worms. The 
possible reasons for our failure to detect these infections will 
be discussed later. 
Leaving aside, for the time being, a discussion as to the patho- 
genicity of the parasites we have encountered, it is perfectly 
clear that they are, to say the least, undesirable guests. The 
utter misery and wretchedness, if not actual suffering, they 
produce, apart from any other harm they may inflict upon their 
unhappy little hosts, are sufficient in themselves to bring about 
a vigorous repudiation and condemnation of the statements made 
in so many textbooks of medicine that these parasites are, for 
the most part, neither important nor particularly dangerous. 
In dealing with the general problem of intestinal parasitism, 
we believe that the parasites may injure their hosts in many 
ways. Among the possible effects that may be produced by 
them are: 
1. The production of antigrowth vitamines or growth-inhibiting sub- 
stances. 
2. The production of substances directly toxic, cytolytic, or hemolytic. 
8. Unfavorable effects upon the host through the liberation of the 
products of metabolism of the parasite. 
4. Mechanical irritation of the mucous surfaces by the parasites when 
present in large numbers. 
