Rothamsted Symposium on Trace Elements xvi 



Investigations on Micro Elements from a Practical Point 

 of View hy F. Steenbjerg, Dr.Agr. (Kgl. Veterinaer- & 



Landboh0jskole, Copenhagen, Denmark) 87 



Determination of Exchangeable Manganese in Soils . . 87 



Copper Values of Danish Soils 90 



"Copper Surface" 92 



Fertilizing Value of Different Copper Minerals ... 93 



Chemical Analyses of Plants 93 



References 95 



Discussion 95 



On the Role of Trace Elements in the Agricultiu-e of Fin- 

 land hy E. A. Jamalainen, Phil. Dr. (Agricultural Re- 

 search Centre, Tikkurila, Finland) 99 



Boron 99 



Sugar Beet C^eta vulgaris v. rafa f. crassa^ 99 



Swede QBrassica napus v. nafohrassica^ 102 



Apple (_Pirus malus') 102 



Clover (TTifolium fratense) 103 



Copper 103 



Manganese 104 



Conclusion 105 



References 106 



Sur TActivit^ et I'lnterdependance des Aliments dans la 

 Nutrition d'Aspergillus niger, Quelques Resultats Ex- 

 perimentaux, far le Professeur J. Lavollay (Conserva- 

 toire National des Arts et Metiers, Paris, France) • • • 107 



Definition du Coefficient d' Action d'un Aliment . . 108 

 Variation du Coefficient d' Action d'un Aliment Suivant 



LA Composition du Milieu Ill 



Discussion 118 



Mode of Action and Occurrence of Trace Elements in 

 Pastures and in the Blood and Liver of Farm Animals 



hy L. Seekles, Ph.D. (Laboratory for Veterinary Bio- 

 chemistry, University of Utrecht, Netherlands) • • • 119 



Trace Elements as Bio-Catalyzers of Enzyme Action . 124 

 The Distribution of Copper in the Liver and the Blood 

 of Cattle and Horses. Regulation of Copper Metabo- 

 lism 124 



Experiments with Cattle 124 



Experiments wntTH Horses 128 



Manganese in Relation to Grass Tetany and Sterility in 

 Cattle. The Occurrence of Manganese in Pasture 



Grass and Hay in the Netherlands 131 



Manganese in Relation to Grass Tetany . . . . 131 



