■ ANNUAL REPORT, 1945-46 SI 



erals. For continuous blood donation a level of iron higher than that used in 

 this study would be advocated. 



2. By Rats. (A. W. Wertz.) The problem of the availability of iron in foods 

 was also studied with the use of the rat as the experimental animal. The foods 

 studied were roast beef and boiled navy beans, both being fed in dry form. Iron 

 sulfate was used as a standard for comparing the availability of iron in these 

 foods. The animals received a basal ration of milk powder and were paired 

 according to sex, weight, litter membership, and hemoglobin of the blood. The 

 amount of iron fed in the supplement was 0.2 mg. per day; and the amount 

 stored during the 35-day period while the rats were receiving the supplement 

 was determined by analyzing the carcasses. 



The rats receiving iron sulfate retained more iron than did their litter-mates 

 receiving the beef or the bean supplements. When the availability of the iron 

 sulfate was set at 100, the retention of iron approximated 60 for the cooked beef 

 and about 90 for the dried beans. These preliminary data suggest that the iron 

 in navy beans may be better utilized than the iron in beef. Contrary to the re- 

 sults obtained with human subjects, the iron sulfate appeared to be a better 

 source of iron for the rat than did the cooked beef. 



Studies Relating to the Cause of Tooth Decay. (Julia O. Holmes, L. R. 

 Parkinson, A. W. Wertz, and B. V. McKey.) The hypothesis used in planning 

 these studies has been (a) tooth decay is caused by the acid which is produced as 

 a by-product of the growth of bacteria which flourish in the oral cavity, and, 

 conversely, decay may be prevented by inhibiting the growth of these bacteria; 

 (b) under certain dietarj' conditions the salivary glands secrete a substance, the 

 anti-caries factor X, which prevents bacterial growth; (c) the factor X either is a 

 constituent of certain foods or is manufactured in the body, possibly in the sali- 

 vary glands, possibly by the bacteria in the digestive tract, from the substances 

 contained in those foods. 



During the year approximately 200 rats have been reared on the decay-pro- 

 ducing diet consisting of coarsely ground corn, milk powder, and alfalfa meal, 

 supplemented with various dietary factors in an attempt to find one which would 

 prevent the rampant tooth decay consistently found in rats reared on this basal 

 diet. These substances included beef muscle, liver, alfalfa, butter fat, yeast, a 

 rice-bran extract, fluorine, the amino acid tryptophane, the vitamins nicotinic 

 acid and K, a mixture of the fat-soluble vitamins, and a mixture of both the fat- 

 soluble and the water-soluble vitamins in crystalline or concentrate form. Other 

 groups of rats were reared on a "purified" diet consisting of casein, mineral mix- 

 ture, a "complete" vitamin mixture, and either sucrose, dextrose, or cornstarch, 

 to determine whether tooth decay can be induced in rats consuming diets which 

 do not contain corn. A sulfa drug, succinyl sulfathiazole, was fed to groups of 

 rats receiving (a) the corn diet in which the corn was Cooked and (b) thepurified 

 diet in which the carbohydrate was starch, both of which had beeii found by other 

 investigators to prevent tooth decay in the rat. The sulfa drug was given be- 

 cause of its "sterilizing" action in tne bowel; the idea being that, if the bacteria 

 of the bowel normally manufacture the factor X from substances in these two 

 diets, the factor would not be made by the rats receiving the drug; hence these 

 rats would experience more tooth decay, than would be found in their litter-mates 

 not receiving the drug. 



None of the supplements fed in conjunction with the raw-corn diet caused 

 even the slightest decrease in the rampant tooth decay observed on the basal 

 corn diet, although some of them had been reported by other investigators as 

 preventing tooth decay. These results led to the tentative conclusion that the 



