SALTS 451 



seeds. When corn, wheat, and rice are highly milled, the 

 polished, or "degermed," corn meal, patent flour, and rice are 

 deprived of the greater part of the compounds of copper, manga- 

 nese, and zinc, which are factors in animal nutrition. In 

 agriculture, some depleted soils require the addition of small 

 amounts of compounds of copper, manganese, and zinc in order 

 to restore and maintain productivity through the supply of 

 necessary vital elements. 



Pernicious anemia was believed to be due to a shortage of 

 iron. Milk is deficient in iron, yet hemoglobin is rich in this 

 metal. It was, therefore, assumed that the way to correct 

 anemia would be to add iron to the milk diet. In the case of 

 animals, this plan proved ineffective. The daily feeding of iron, 

 administered as chloride, sulphate, acetate, citrate, or phosphate 

 in the milk, all prepared from pure iron wire, did not check a 

 decline in hemoglobin content of the blood. Rats suffering with 

 anemia were not improved. But when they were fed dried 

 liver, the ash of dried liver, corn, or lettuce, which contain iron 

 and copper, the hemoglobin was raised to normal, and the 

 stricken rats immediately restored to health. E. B. Hart found 

 that when copper sulphate is added to pure iron chloride in the 

 whole-milk diet, cures result. Rats, so anemic that their days 

 appeared to be numbered, recovered immediately, and the 

 hemoglobin in their blood was brought to normal. 



The role of copper in animal life is probably similar to that of 

 iron in plant life. Hemoglobin does not contain copper, and 

 chlorophyll does not contain iron, yet copper promotes the 

 building of hemoglobin, and iron promotes the production of 

 chlorophyll. Both function as catalysts. 



The distribution of salts in the body is not uniform. Con- 

 centration and similar gradients result. A salt gradient must 

 inevitably mean an osmotic and an electric potential gradient 

 and is strong evidence of a metabolic gradient. The conductance 

 (page 337) of samples of plant sap squeezed from tissue at several 

 points along the plant should indicate a gradient if one is there. 

 Hurd-Karrer used specific gravity as an indicator and found that 

 the juice of corn stalks taken from successive internodes showed 

 a progressive increase in specific gravity from the ground up. 

 Similar salt gradients have been reported in trees by a number of 

 workers. 



