l62 H. C. BRADLEY 



have thus far found to utilize the element manganese is the 

 Unionidse, the common fresh-water mussels. Since 1906 when 

 the element was first noticed in the specimens obtained from 

 the Madison Lakes of Wisconsin, 1 we have examined many 

 hundreds of specimens from the Mississippi basin, St. Lawrence 

 and Atlantic coast drainage. In not a single specimen has the 

 element been wanting or small in amount. It is obvious that a 

 single individual which failed to show manganese, or contained 

 only a trace of it would be sufficient to cast grave doubts upon 

 the normality of the element and lead one to ascribe an adven- 

 titious character to it. But in every case manganese has been 

 abundant. The reactions for its identification are fortunately 

 brilliant and decisive and at the same time indicate very well 

 the relative amount of the element. The quantitative deter- 

 minations show that the metal occurs in quite uniform amounts 

 in the various specimens examined. 



To summarize briefly the results: Some twenty-four analyses 

 were made quantitatively upon material from about Madison. 

 Some of these analyses were made upon single specimens of 

 Anadonta or Unio, more were made upon a sample taken from 

 the dried and pulverized tissues from a large number of speci- 

 mens secured at one time from a given locality. Many of these 

 analyses therefore represent the average of fifty or a hundred 

 individuals. The average of the twenty-four analyses shows 

 21.8 per cent, of ash in the tissues, 4.52 per cent, manganese 

 present in the ash and 0.95 per cent, manganese in the tissues. 

 Mussels from the Wisconsin River averaged about 14.5 per cent, 

 ash, 2.4 per cent, manganese in the ash and 0.35 per cent, in 

 the tissues. From the Temagami Reserve of Ontario mussels 

 averaged 15.4 per cent, ash, 3.1 per cent, manganese in the ash 

 and 0.45 per cent, in the tissues. Specimens obtained from a 

 great number of localities in Michigan, Illinois, Wisconsin, 

 Indiana and Iowa average about 17.0 per cent, ash, 3.4 per cent, 

 manganese in the ash and 0.60 per cent, in the dry tissue. A 

 number of normal, average sized specimens from Lake Mendota 

 were dissected into their more prominent tissues or organs. 

 Analyses of these fractions gave the following results: 



1 Bradley, Jr. Biological Chem., III., 151, 1907. 



