MINERAL METABOLISM OF FARM ANIMALS                       281

to K by addition of sodium salts to a cereal ration, and have found that the addi-
tion of sodium chloride or sodium citrate led to increased assimilation and retention
of nitorgen calcium and phosphorus. In a later paper ²⁶ it was found that the
addition of potassium citrate to the diet decreased the retention of the
above constituents. With regard to lime retention, potassium citrate led to a
decrease while sodium citrate showed an increased retention and the authors conclude
that a high Na : K ratio may have a considerable influence on the calcium assimilation,

THE INTER-RELATION BETWEEN ORGANIC AND INORGANIC CONSTITUENTS OF THE
                                                    DIET.

The first point that arises in this connection is the rôle of organic constituents
on the retention of minerals and secondly the rôle of minerals in the phenomenon of
digestion and absorption of the energy producing substances. Thus Auchinache ²⁷
in a recent series of elaborate experiments with sheep finds that there is some
unidentified substance in green pasture which is superior to cod liver oil in assisting
assimilation and retention of lime and phosphoric acid. Godden and others ²⁸ find
that with pigs on a ration badly balanced with respect to CaO and P₂O₅, the addi-
tion of oils like cod liver oil, linseed oil and olive oil caused a rise in the calcium and
phosphorus balances.

The question of the rôle of minerals on the digestion and assimilation of the
organic constituents of the food has not been throughly studied, but the results
obtained by Förster ²⁹ are significant. When minerals were previously extracted
from the food, he found that on this diet dogs died sooner than in complete starva-
tion. Signs of disturbance of the digestive organs appeared early. They were soon
accompanied by increased excitability and weakness of the neuromuscular system.
The central nervous system was also affected, as was shown by the occurrence of con-
vulsions and periods of drowsiness. A remarkable feature of the experiments
was the profound disturbance caused by relatively small losses of inorganic salts
from the system. The total mineral matter of the body at the beginning
of the feeding with the diet from which all salt had been extracted was
estimated at 1500 grams. During the experimental stage, the body lost phos-
phoric acid and sodium chloride in greatest amounts compared with other minerals,
but the actual amount of loss of these minerals was only 30 grams and 7 grams
respectively before death occurred as a result of mineral starvation. A well
nourished body could lose a far larger proportion of its total protein, fat or
carbohydrate without showing any marked disturbance of its functions.³⁰

Regarding the effect of minerals on intestinal absorption, recent experiments by
the writer ³¹ on the rôle of blood calcium on carbohydrate metabolism point to some