RELATIONSHIP OF PICA IN CATTLE TO TRYPANOSOMIASIS    77

Analyses of Bones of Untreated Animals.

The ash to organic matter ratio is clearly one of a rachitic or osteomalacic
character (adult rickets), Merely the fact that the skeleton is fully grown pre-
vented any of the stigmata of rickets being present. As the animals had grown
to adult form in the normal manner, these analyses can only mean that there was a
tremendous loss of calcium phosphate going on from the bones before the animals
finally succumbed to the loss. Physically it was observed that the cortical portions
of the bones were much thinner than the corresponding bones from the slaughter
place.

Hutyra and Marek (1926, third edition) remarked that any calcium deficiency
is aggravated by any excess of phosphoric acid in the dietary, as this merely
causes a further excretion of calcium. The tendency appears, on average, with
many exceptions, for plants to be much richer in phosphorus than calcium in
Nigeria, and so there is a strong probability that any calcium deficiency in the
herbage is intensified by the higher proportion of phosporic acid present, even
though, as has been pointed out, the phosphoric acid present is really in itself
deficient in amount.

But calcium deficiency, whatever its cause, cannot cause any drain on the
pre-formed long skeleton except under certain conditions. Bunge's hypothesis that
potassium salts in excess lead to an abnormally high excretion of sodium salts
is generally used to explain the craving of livestock for sodium chloride. This
hypothesis seems to depend on the generally accepted fact that livestock are not
likely to suffer from deficiency of potash when fed on any type of pasture, while all
grasses tend to be poor in sodium. Another reason for the drain of sodium from
the system is a dietary in which there is a marked acid imbalance. A large acid
supply with a low alkali content of the blood will lead to a combination of sodium
and postassium with these acids, and so the combining power of the calcium ions
present is reduced merely by the absence of substances with which to combine.

Were the cause of the pica the very low calcium content of the feed, we should
have found that bone meal would have stopped the disease. Salt and bone meal,
however, did stop the condition in Group III. Now Foster has pointed out the

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