consumed be measured. Also that in all such experimentation it is
necessary to run controls on a complete diet rather than to rely too much
on standard figures. For this latter purpose it is merely necessary to add
to the basal diets the "A" as butter fat and the "B" as dried yeast or
otherwise to make them complete. Various special mixtures have been tested
out for this purpose and the data already presented supplies the
information necessary to construct such control diets. Professor Sherman
has given me the following as a control diet on which he has raised rats
at normal growth rate to the fifth generation:

One-third by weight of whole milk powder.
Two-thirds by weight of ground whole wheat.
Add to the mixture an amount of NaCl equal to 2 per cent of the weight
of the wheat.

A control mixture based on Osborne and Mendel's data would have the
following components:

Meat residue 19.6 per cent or casein 18 per cent.
Starch 52.4 per cent or 49 per cent.
Lard 15 per cent or 20 per cent.
Artificial protein-free milk 4 per cent.
Butter fat 9 per cent.
Dried yeast 0.2 to 0.6 gram, daily.

The preceding description has applied especially to testing for the
presence of the "A" or the "B" vitamine. When we come to the methods of
testing for the "C" type it is necessary to change our animal. Rats do not
have scurvy but guinea pigs do. The philosophy of the tests for the
antiscorbutic vitamines then will be identical with that of the