CATALYSIS: THE GUIDE OF LIFE 119 



solid 44 called turacin. This has been recently proven to be a copper 

 porphyrin compound. 45 Over sixty years ago Professor James F. W. 

 Johnston (University of Durham, England) made the following com- 

 ment: 46 



"The existence of an animal pigment so rich in copper as turacin 

 (about 8 per cent), offers many interesting problems for study. Traces 

 of this metal seem generally diffused in most vegetables and many 

 animals; but here are more than traces — weighable and visible quanti- 

 ties. It is true that these plantain-eaters have been seen to pick up in 

 their native countries grains of malachite, the green mineral carbonate 

 of copper; but we must rather look to the vegetable food they con- 

 sume as the true source of this metal. And when the copper is 

 ingested, how does it find its way, in the complex pigment of which 

 it is an essential part, precisely to those feathers, and to those barbs of 

 feathers, and to those parts of such barbs, which are red, and not to 

 the black portions? For if one of these feathers is burnt in a Bunsen 

 gas-burner, not till the red part of the feather is reached will the green 

 flash of the copper tinge the flame. However, in the crest of the violet 

 plantain-eater (Musaphaga violacea) and perhaps traces in blood of all 

 these birds, turacin, and therefore copper, does occur. Still the whole 

 mystery of this strange pigment is far from being understood." 



It has recently been reported that certain molds will not grow in the 

 absence of traces of gallium; and Aguilhon and Sazerac 47 found that 

 the addition of 0.0001 per cent of uranium acetate to a fermentation 

 mixture of Acetobacter suboxidans and sorbitol increased the yield of 

 sorbose by 76 per cent. 



In an article on the biochemistry of microorganisms C. B. Van Niel 48 

 refers to many other cases where trace substances are vital: e.g., 

 molybdenum for the nitrogen-fixing organism Azobacter; copper for 

 common molds as well as for higher plants; boron, apparently needed 

 to form borocitrin, related to the flavin pigments and found in micro- 

 organisms by Kuhn. Van Niel also tabulates the recent work of vari- 

 ous investigators showing the diverse ways in which different organ- 

 isms split acetate and normal butyrate. 



E. C. Auchter, 49 Chief of the Bureau of Plant Industry, U. S. Dept. 

 of Agriculture, in discussing the interrelation of soils and plant, ani- 

 mal and human nutrition, lists some of the "physiological troubles" 

 of plants which can be cured by supplying the necessary small amounts 

 of certain missing but essential elements. It must, of course, be re- 

 membered that larger amounts than the tiny optima may be very 

 harmful, as is the case, e.g., with boron. Magnesium cures sand drown 

 of tobacco in the soils of the coastal plain; manganese cures chlorosis 

 of tomatoes on some calcareous Florida soils, and permits such soils to 

 give improved yields of potatoes, snapbeans, cabbage, lettuce, peppers, 

 carrots, beets, citrus and corn; zinc cures pecan rosette in the South, 



