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     It may be accepted with regard to salt metabolism that, like protein, its level
is determined by supply—with this difference that, whereas protein may be very
defectively absorbed, salt is under ordinary circumstances almost completely ab-
sorbed by the intestinal tract. There is a widespread belief that, in consequence
of man's habit of consuming an extravagant amount of salt, a certain superfluity
of it remains in the body. How large this excess from salt consumed may be is
best seen from investigations in which its disappearance can be traced, as in
fasting or in abstinence from sodium chloride alone.¹

     From observations on professional fasters who, previous to the period of
fasting, had contented themselves with moderate quantities of common salt—about
10 grammes daily—the amount of salt given off by the body during the fast was
estimated at 17 or 18 grammes. It has not been absolutely determined whether
larger amounts are amassed in the body in cases where salt is taken in larger quan-
tities—20 to 25 grammes. It is very probable, however, that such is the case. The
effect of placing an animal on large quantities of sodium chloride has been shown
to cause an increase of body-weight, which can only be explained by a retention of
water in sufficient quantity to dilute the salt retained to a solution isotonic with
the fluids of the body. The opposite holds true to an even greater extent; for,
while salt equilibrium may become established so quickly on increasing the amount
of salt that no, or only a slight, increase in body-weight results, the effect of de-
creasing or stopping salt altogether is to cause at once a loss in body-weight which
is greater than can be accounted for by loss of flesh, and is due to water being lost
together with the sodium chloride. That is, when the administration of salt is
largely decreased or stopped the excretion of chlorides in the urine is greater
than the salt intake so that the body becomes poorer in salt, and less water is
required to maintain the isotonicity of its solution: the body-weight therefore
falls.

     We shall consider the effects of the large sodium chloride intake of the pri-
soners on body-weight, diuresis and number of red blood corpuscles. We shall
also give some observations on the effect of the large salt intake on its elimina-
tion by the fæces and skin.

Investigations to determine the effects of large quantities of salt on :—

¹ Von Noorden, The Physiology of metabolism.

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