Effect of Manganese Compounds 91 



experiments showing its constant presence in a ferment (laccase) obtained 

 from plants. He also extracted from lucerne a substance very poor in 

 manganese, which was somewhat inactive, but which regained or increased 

 its activity on the addition of manganese. Bertrand stated that manganese 

 was apparently not to be replaced by another metal, not even by iron, 

 and that the small quantity of it occurring was no reason for regarding 

 it as a secondary element in the composition of plants. The view was 

 also put forward that in the presence of certain organic substances, such 

 as hydroquinone, pyrogallol or similar bodies, manganese is capable of 

 fixing free oxygen from the air, the volume of oxygen absorbed varying 

 according to the compound of manganese used. Bertrand was led 

 to conceive the oxydases as special combinations of manganese in 

 which the acid radicle, probably protein in nature and variable ac- 

 cording to the ferment considered, would have just the necessary 

 affinity to maintain the metal in solution, i.e. the form the most 

 suitable for the part it has to play. The manganese would then 

 be, according to his view, the true active element of oxydase, which 

 functions as the " activator " ; the albuminous matter, on the other 

 hand, gives to the ferment those special characters, which show 

 themselves in their behaviour with regard to reagents and physical 

 agents. From this point of view manganese could no longer be con- 

 sidered as a non-essential element, but as a substance of vital 

 necessity to the functions of plant-life. The name "complementary" 

 manure was suggested for compounds of such elements as manganese, 

 which exert a physiological action and which were proposed for use 

 as manures. Later (1905) Bertrand considered that he had still further 

 proved the indispensable nature of manganese. The absence or insuf- 

 ficiency of one essential element arrests or diminishes growth. This 

 applies not only to those substances which are present in the greatest 

 abundance, such as C, P, N, &c., but also to those elements like man- 

 ganese, boron, and iodine, which only occur in traces. These elements 

 are usually specialised in function, and for them the name " catalytic " 

 elements was suggested, in view of the work they are held to do. As 

 late as 1910 the role of manganese in the functioning of the oxidising 

 enzymes was again insisted on. It was concluded that manganese 

 intervenes as a catalytic agent in the material changes of which 

 plants are the seat, and that it participates in an indirect manner 

 in the building up of the tissues and in the production of organic 

 matter. 



