LOUIS FREEDMAN 15 



It is quite possible that the nature and reaction of the media 

 play an important role in these adsorption experiments. Inhibit- 

 ing substances may also be present, so that a solution may be 

 active after adsorption, although inactive before that procedure. 

 How important this hypothesis is, we cannot at present state, as 

 we did not fully investigate these solutions before extraction with 

 the adsorbents. 



A summary of the results obtained shows that the substances 

 which promote the growth of bacteria and yeast (as extracted 

 from beef-heart, peptone, autolyzed yeast, etc.) belong to the 

 class of vitamines of the water soluble B type ,but are not identi- 

 cal with B vitamine; that they are comparable in activity and 

 show similar properties in that they are easily extracted from 

 their natural sources by the same adsorbents, and are again 

 readily recovered from these adsorbents without appreciable loss 

 in activity. These results point strongly to the conclusion that 

 they are either identical with vitamine D, or so similar to it in 

 their physiological behavior, that only by actual isolation, purifi- 

 cation, and complete chemical analysis will it be possible to differ- 

 entiate them. 



The separation of these vitamine-like substances from the 

 bulk of impurities with which they are associated in nature, by 

 adsorbing them in fullers earth and norit and their subsequent 

 extraction by chemical treatment of the adsorbents, gives us 

 these unknown substances in a highly concentrated and com- 

 paratively pure form. This procedure is a distinct advantage 

 over working with these substances in their natural media. 



SUMMARY OF CONCLUSIONS. 



1. There are present in beef and beef -heart infusions, pep- 

 tone and autolyzed brewer's yeast, certain substances which show 

 a strong growth-stimulating activity on both hemolytic strepto- 

 cocci and yeast cells. 



2. These active substances can be extracted from their na- 

 tural sources by shaking with certain adsorbents, such as ful- 

 lers earth and norit charcoal, and can be recovered by extract- 

 ing the adsorbents with baryta and acetic acid respectively. 



3. The properties of these substances show them to be of a 

 vitamine-like nature ; and they are either identical with the vita- 



