28 MASS. EXPERIMENT STATION BULLETIN 347 



to date indicate that a 32° C. incubation temperature gives more accurate counts 

 than the standard 37° C. temperature. The Bowers-Hucker plating medium 

 does not appear to have any advantages over the standard medium when incu- 

 bation is at 32° C. 



A Comparative Study of Proposed New Methods and Standard Methods 

 for Testing Oysters. (Ralph L France.) This project has been undertaken upon 

 the request of Dr. C. A Perry, referee and chairman of the Standard Methods 

 Committee for Oyster Analysis of the American Public Health Association. 

 Work will be started as soon as a copy of the proposed new methods has been 

 received from the referee. 



Influence of Added Iodine and Kelp on Intestinal Flora of White Rats. (W. B. 



Esselen, Jr., James E. Fuller, and George S. Congdon.) It is generally conceded by 

 authorities that the aciduric bacteria of the acidophilus type are preferable in the 

 intestine to bacteria which decompose protein materials, since the latter produce 

 products which are detrimental to the body when they are absorbed into the 

 blood. This project was designed to study the influence of iodine and mineral 

 elements and their salts on intestinal bacteria. 



White rats were fed raw or pasteurized milk, both with and without added 

 iodine. A similar experiment was run with kelp instead of iodine added to the 

 milk. The addition of iodine or kelp to the milk did not appear to influence the 

 ratio of aciduric to proteolytic bacteria. All of the milk diets increased the per- 

 centage as well as the numbers of aciduric bacteria; raw milk without iodine was 

 less effective than were the other milk diets. There was no marked effect on the 

 reaction (pH) of the feces of any of the rats. Gastric acidity of rats on the kelp 

 supplement was higher than that of rats not fed kelp. Kelp in the diet did not 

 significantly influence the amount of urinary phenol (considered indicative of 

 intestinal putrefaction) or of conjugated phenols (considered indicative of the 

 ability of the body to neutralize toxic phenols absorbed from the intestine). 

 This is the completion of the study reported previously (Mass. Expt. Sta. Bui. 

 339, 1937). 



Influence of Added Iodine on the Bacterial Flora of Milk. (George S. Congdon 

 and James E. Fuller.) The influence of added iodine on the bacterial flora of 

 milk was investigated. In addition, pure culture studies were made with bacteria 

 inoculated into sterilized raw milk and into nutrient broth. Tincture of iodine 

 U. S. P., Gram's iodine-potassium iodide solution, and Iodine Suspensoid (Merck) 

 were the forms of iodine employed Gram's iodine solution was a somewhat 

 more efficient germicide than the other two solutions, but it is less stable. Milk 

 with a higher bacteria count required more iodine for its sterilization than did 

 low-count milk. This is the completion of the study previously reported (Mass. 

 Expt. Sta. Bui. 339, 1937). 



The Action of Intestinal Bacteria on Ascorbic Acid (Vitamin C). (W. B. Esselen, 

 Jr.) The purpose of this study was to investigate the reported destruction of 

 Vitamin C by certain intestinal bacteria, and to attempt to discover the mech- 

 anism of the vitamin's destruction. Pure cultures of the bacteria employed were 

 cultivated in media containing ascorbic acid. The results indicated that, instead 

 of destroying Vitamin C, the bacteria actually exerted a protective action which 

 varied directly with the suitability of the medium for bacterial growth and with 

 the numbers of bacteria present. Lowered pH in the medium was not a factor in 

 protecting the vitamin, and no correlation was observed between the ability of 



