390 AXXALS XEW YORK ACADEAIY OF SCIEXCES 



tion with, potassinm selenate was slight in comparison with that prodnced 

 with sodiTim selenite and but few grannies were found scattered in the 

 spleen, pancreas and liver. In the case of potassium selenocyanate, re- 

 duced selenium was found in the liver, spleen, lung, kidnev, pancreas, 

 heart, brain (only in hemorrhagic spots), muscle (only in similar spots) 

 and stomach. 



The reduction of selenium compounds seems to be a detoxicating 

 process, since selenium itself is hardly poisonous. It seems evident that 

 while sulfur compounds, such as sodium sulnte, are oxidized in the body 

 to sulfate, the corresponding selenium compounds, such as sodium sele- 

 nite^, suffer reduction. 



LIVIXG BACTEEIA 



Living bacteria bring about the reduction of selenious acid, selenic 

 acid and sodium selenite. The precipitated selenium follows the path 

 of bacterial growth. Granules of selenium can be observed under the 

 microscope within the bacterial cell. The medium used should not con- 

 tain reducing chemical substances, such as glucose or lactose. Sodium 

 selenate is not reduced. Due to decomposition induced by acids, selenium 

 may be also deposited from pot-assitmi selenocyanate. This happens to 

 be the case with B. coli. 



Eeduction is proportional to the intensits' of growth. Selenious acid, 

 selenic acid and, less markedly, sodium selenite do not favor growth. 

 The amount of retardation depends upon the nature of the organism. 

 Streptococcus pyogenes was found to be more sensitive tlian BaciUus coli. 

 The bacilli of symptomatic anthrax, edema, and tetanus are retarded very 

 markedly in growth. Sodium selenate and potassium selenocyanate do 

 not retard growth. 



Selenium dioxid or sodium selenite cannot be used as a differential 

 test between srobic and anarobic organisms, since the latter class also 

 bring about reduction. There seems to be no specific relationship be- 

 tween selenium reduction and hydrogen sulfid production as Gloger 

 maintained, since micro-organisms, such as B. acidi Jactici. B. dipth- 

 thericBj, B. pseudo-diphtheruF^. B. tuberculosis that produce no hydrogen 

 sulfid or only traces, were capable of reducing selenium dioxid or sodium 

 selenite. 



For practical purposes selenium dioxid or sodium selenite in concen- 

 trations of 1 :50,000 or 1 :25,000 can be used to demonstrate bacterial 

 reduction. This phenomenon can also serve as a qualitative test for the 

 selenite ion, even if the seleniotis acid or the sodium selenite is present 

 in culture media in such small concentrations as 1 :100,000. 



