ISOTOPIC INDICATORS IN HAEMATOLOGY 645 



enhancement attained is only temporary. A more permanent increase 

 of the iron content in the plasma is spoiled by the fact that an increase 

 of the iron level is accompanied by an increased rate of escape of iron 

 from the plasma and, therefore, an increased rate of entry of iron from 

 the organs is required to maintain the increased level of iron. By the 

 oral administration of iron tartrate Laurell^**^ attained almost double 

 the iron content in the plasma of a healthy person, but the normal 

 plasma-iron level was re-established after 20 hr. After the injection of 

 10 mgm of iron, ToTTERMAN^"^ found the 2 hr value to be only about 15 

 per cent less than the 5 min value, indicating a partial compensation 

 of the escaping plasma iron by the iron from the organs. 



We found the daily metabolism of plasma iron^^'^ in a rabbit weighing 

 2.6 kgm to be about 800 //gm; of this somewhat more than 400 jugm is used 

 to replace the decayed blood corpuscles while only 80 ^gm is taken up 

 by the liver. The 400 //gm of iron which is used daily for forming haemo- 

 globin appears again after the decay of the blood corpuscles which 

 contain this compound. Only small amounts of iron are absorbed daily 

 by the digestive organs. 



The daily uptake of iron of the liver, which contains 7 mgm iron, from 

 the plasma amounts to 80 //gm and this must be compensated hj a corre- 

 sponding release to the plasma since, otherwise, the iron content of the 

 liver would be doubled in the course of 3 months. The liver takes up 

 these small quantities only from the transferrin of the plasma; in a period 

 of 6 hr the liver absorbs almost one-half of 0.5 mgm of iron salt injected 

 into a rabbit. Of 1.6 gm of "ferrivenin" injected, 84 per cent was ofund 

 in the liver of an infected patient^24) 



The liver of a rabbit which had been injected for several months with 

 iron (viviferrin) and which had an iron content of 35 mgm absorbed only 

 40 //gm daily from the plasma^i"\ The iron turnover in the plasma of such 

 rabbits is greater than in normal animals. A 30 per cent higher content 

 of haemoglobin, 12.9 gm % instead of 9.8 gm %, with an almost unchanged 

 content of plasma iron, 151 //gm % instead of 145 //gm %, was essentially 

 responsible for the increased metabolism from 800 to 920 //gm %. 



It is not likely that a liver burdened with iron will release less iron 

 than a normal one, and since it absorbs less from the plasma than does 

 the latter, some latitude becomes available for the release of its iron 

 burden. An investigation by ANDERSON^i^Undicates that this does occur. 

 While 18.4 mgm % iron was present 3 months after injecting iron into 

 a liver burdened with iron, the content decreased to 16.1 mgm % after 

 6 months. 



Generally the liver is regarded as the main organ for storing iron, 

 and the ferritin of this organ as the compound which yields iron to the 

 plasma. Mazur and his co-workers^i^> have recently produced a proof 

 that a small portion of the ferritin iron is present on the surface of the 



