23
The Carbohydrate of the food-stuffs analysed was estimated
by completely changing all the carbohydrate material into sugar
by the action of hydrochloric acid, and then estimating the per-
centage of sugar by Fehling's method, checking the results by
the Pavy-Fehling method or the Picro-Saccharometer.
The Fat was estimated in the usual way by means of
a slightly modified Soxhlet apparatus manufactured to our
drawings by Messrs. Baird and Tatlock, London.
The moisture and ash require no comment.
II. The method of procedure when we came to investigations on prisoners
was almost invariably to use as our unit a batch of five picked
prisoners—in a few cases we had four in the batch, in some
six and in some ten. The excreta from these five men—or from
the batch—were pooled, and in every case two samples of the urine
and two of the fæces—when examined—were put up fór nitrogen,
and a sample of each for chlorides; one of the urine for ammonia
and sometimes the urea, phosphates, purin bodies, etc., of the
urine were also estimated. The specific gravity and reaction of
the urine was always taken. The weight of the prisoners making
up the batch was taken every day; it was noticed that while
individual prisoners varied in weight from day to day, the average
weight of the batch after the first three or four days remained
practically constant.
The prisoners to form the subjects of the investigations having
been chosen, were isolated from the other prisoners. In the larger
jails we were able to make use of a block of cells with a common
yard where the work given to the prisoners could be carried out,
and where they were able to get air and exercise while at the
same time the facilities for feeding and collection of excreta were
much greater than was the case in the smaller jails. In the
smaller jails a large block of cells was not available for this
purpose; we were always able however to obtain some godown
or store for the isolation of the batches.
The next step was to put the batches on the diet that we wished
to investigate. This was usually done for some days before any
collection of the urine and fæces for analyses was made, in order to
give time for the proper amount of protein to be absorbed and
nitrogenous equilibrium to be established, and to allow of the usual
increase in body-weight which we found to occur when the
prisoners were first put on a diet weighed and distributed by us.