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THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VII, IV
Another method of testing the influence of carbohydrates on balantidia was
to inject starch in either gelatinized or granular form into the caecum of infected
rats. In every case the number of balantidia increased greatly within a short time,
whereas no increase in numbers occurred in the control animals. During these
experiments both division and conjugation were noted among the balantidia,
but no cysts were observed. The conclusion reached was that rats might become
infected in nature if they were to ingest balantidia and were to subsist on a diet
containing from 60 to 93.5 per cent of carbohydrates. They could not transmit
the infection to other rats, however, since infective cysts apparently are not
formed within the intestine of the rat.
Confirmation of these experimental results was obtained when caecal material
from 79 pigs was analyzed. It was found that heavy infections with balantidia
were generally accompanied by a diet high in carbohydrates in the form of grain.
Large quantities of undigested carbohydrates and an intestinal flora such as would
develop on a high carbohydrate diet were found in these animals and absent from
pigs that were either negative or exhibited light infections with balantidia.
Heavy infections with balantidia were accompanied by larger numbers of aciduric
organisms and lesser numbers of lactose fermenters and proteolytic anaerobes, and
light infections were accompanied by a lesser number of acidurics and a greater
number of lactose fermenters and proteolytic anaerobes.
At about this stage in our investigations an observation was made that
directed our attention to another phase of the subject. We were fully aware of the
fact that dysentery amoebae thrive better in a medium containing starch than
in media free from starch and actually ingest starch grains. We found also that
trichomonads will ingest starch grains and grow and multiply best in cultures to
which this carbohydrate has been added. But not until we placed starch grains
in a culture containing balantidia and then watched them under a microscope
did we realize how voracious a protozoon can be. These balantidia did not ingest
them one by one and at infrequent intervals but swallowed many of them at a time
and soon became so gorged with them as to reach twice their normal size. Within
15 minutes 100 per cent of the balantidia had. ingested starch grains.
This astonishing observation suggested to us that perhaps starch is used
largely as food for the balantidia, and hence, when the host is fed on a high protein
diet, these ciliates starve to death. A plan to test this hypothesis was soon deve-
loped. This included a study of the correlation between the amount of carbo¬
hydrates in the intestine and the number of species and individuals of intestinal
protozoa. Guatemala was selected as the scene of our activities since the natives
of tropical America are known to harbour large numbers of intestinal protozoa
and to live on a diet consisting largely of carbohydrates.
We first had to devise a method of determining the presence and quantity
of starch in human faeces. This proved to be a real problem in. itself. Then we