Nutrition Investigations. 



329 



Marked evidences of change were observed in one trial with a putre- 

 factive mixture (on dulse), and in some of the four-week cultures. 



Irish moss was the most thoroughly investigated and proved the 

 most resistant. In the long experiments (4 weeks) where the other 

 carbohydrates suffered more or less change this one remained appar- 

 ently unaltered. The results of this series are summarized in the 

 following table: 



Irish Moss. 



The single experiment with the galactan, limu manauea, under the 

 same conditions, with the inixture of pure aerobes, gave similar 

 results, but the fact that liquefaction occurred in the peptone-beef 

 extract culture medium after exposure to the air, shows that general 

 conclusions as to the behavior of galactans cannot be drawn from 

 study of a single representation of the class. We have, however, 

 further proof that the galactans are not easily decomposed by bacteria, 

 in the fact that aqueous solutions of all the galactans included in the 

 present series, could be left several days in the warm atmosphere of 

 the laboratory without any apparent change taking place; and in the 

 fact that agar-agar, so widely used in bacteriological laboratories 

 on account of its indifference to bacterial action, is a member of the 

 galactan group. It has been suggested^ that extracts of other sea- 

 weeds might prove good substitutes for agar-agar as culture media, 

 if fully investigated. So far, the greatest objection to use of Irish 

 moss in this way is that it tends to liquefy at body temperature; 

 strong solutions (4 per cent) can, however, be kept fairly firm at a 



»Cf. Reed (18). 



