52 MASS. EXPERIMENT STATION BULLETIN 436 



corn diet may produce decay, not because of its deficiency in factor X but be- 

 cause it contains some deleterious substance which either unites with factor X 

 thus making it unavailable, or makes impossible the synthesis of factor X. Un- 

 expectedly, tooth decay was present in an advanced state in the rats receiving 

 the cooked-corn diet, although the incidence and extent of decay were not as 

 great as on the raw-corn diets. This led to the conclusion that corn causes decay 

 in the rat, not because of the hardness of the particle but because of some funda- 

 mental constituent either in the corn or lacking in the corn. If corn contains a 

 deleterious substance, it is not found in the starch fraction of the corn, since rats 

 fed the purified diet containing cornstarch did not experience tooth decay. 



The replacement of cornstarch by cane or corn sugars in the purified diets 

 resulted in a mild degree of decay on the grinding surfaces of the teeth. This is 

 the first report of such a finding in the albino rat fed purified diets, although it 

 has previously been repgrted that the cotton rat develops tooth decay when 

 subjected to diets containing soluble carbohydrates. The fact th£.t the soluble 

 carbohydrates when fed in large quantity allow tooth decay might tempt one to 

 conclude that the sugars are the sole cause of decay. Such a conclusion must be 

 abandoned, however, in view of the rampant decay found in rats fed corn diets, 

 which contain only a small amount of soluble carbohydrate — the lactose in the 

 milk powder. 



The sulfa drug did not increase the incidence or extent of decay over that 

 found in litter-mates receiving the diet without the drug. None of the rats 

 receiving the purified diets showed decay even though they received the sulfa 

 drug. Likewise the cooked-corn diet plus the sulfa drug was not any more con- 

 ducive to decay than the diet without the drug. These findings suggest that 

 either factor X is not manufactured by the bacteria in the bowel, or the sulfa drug 

 in the dosage administered does not prevent the growth of the strain of bacteria 

 responsible for its manufacture. 



Although the year's work has not resulted in data which confirm or refute the 

 hypothesis used in planning these experiments, the study will be continued. 



The Role of Calcium in the Calcification of Bones. (Marie S. Gutowska and 

 Julia O. Holmes. ) In a preliminary study of the influence of environmental 

 temperature on calcium metabolism, growing rats held at 62 °F. consumed ap- 

 proximately twice as much food as did litter-mates held at 87°. On analyzing 

 the carcasses of the rats, more calcium was found in those held at the cold tem- 

 perature and it was concluded that the cold temperature stimulated the storage 

 of calcium in the rat. However, since the animals in the cold environment con- 

 sumed twice as much food as those in the warm, and since the percentage of 

 calcium in the ration was identical for both groups, it is obvious that the animals 

 in the cold environment consumed twice as much calcium. Consequently the 

 results obtained might have been due to differences in quantity of calcium con- 

 sumed rather than to differences in environmental temperature. In order to 

 distinguish between these two variables, temperature and quantity of food eaten, 

 a system of feeding was devised whereby the animals of two groups would re- 

 ceive equal quantities of calcium but would be allowed to eat as much of the 

 calcium-free basal food as was necessary to satisfy individual needs. 



In Series 1, two litter-mate groups of animals, one held at 62°F. and the other 

 at 87 °F, were fed a diet containing 0.6 percent calcium. All were allowed to 

 eat as much as they desired. In Series 2, three litter-mate rats were fed a small 

 portion of calcium in a fixed daily quantity separate from the ration, which was 

 devoid of calcium. One rat was allowed to eat as much of the calcium-free food 

 as he desired, the second was allowed only three fourths as much food as the 

 first, and the third was allowed only half as much as the first. In Series 3, two 



