We have estimated the iron balance in six dogs before and after splenectomy, in two intact dogs, and in five dogs before and after major operations other than splenectomy.

In all the animals studied, considerable variation in iron balance was observed in the periods used (6 to 14 days). The intact controls had positive balances, the one followed for a year and a half having over 0.4 mg. per kilo per day, except when fasting or on an inadequate intake. The iron of urine, lost hair, dandruff, etc., which was not included in the determinations, would be far from sufficient to restore equilibrium.

Of five animals subjected to major operations other than splenectomy, all of which in preoperative periods had positive balances varying between 0.423 mg. to 0.075 mg. per kilo per day, three showed a positive balance of from 0.989 mg. to 0.057 mg. and two showed negative balances of from 0.02 to 0.18 mg., the last two having anemia in the period of study while the others had none.

Of the six splenectomized dogs, five showed a greater tendency to loss of iron after splenectomy (i.e., either a change from a positive to a negative balance or to an increasedly negative or lessened positive balance). This was not always apparent until some days after splenectomy and coincided approximately with the period of developing anemia. The removal of the spleen was usually found therefore to be transiently associated with increased excretion of iron. It is not possible to demonstrate, however, that the increased loss of iron is the cause of the anemia, and the matter awaits further investigation before the reason of its occurrence is made clear.

An adequate iron intake in an intact animal was usually accompanied by a positive balance, though in splenectomized animals during the period of anemia it was frequently accompanied by a negative balance. Gain in weight in intact animals likewise was associated with a positive balance; but in the three instances in which gain of weight occurred during periods of anemia, after splenectomy or other operations, it was associated with a negative balance. Weight maintenance was also associated with a positive balance except in one instance of severe postsplenectomy anemia. Loss of weight was not sufficiently associated with a negative balance to make it seem a definite factor influencing the balance, per se, although about one-third of the periods of loss of weight were associated with negative balances.

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