24 MASS. EXPERIMENT STATION BULLETIN 374 



Experimental Procedure 



In the series of experiments reported here, an attempt was made to 

 produce atherosclerosis under carefully controlled conditions in rabbits 

 of known age and litter, and to study the efifects of various forms of iodine 

 and other inorganic substances in the ration upon the severity of the 

 aortic damage as related to blood cholesterol. Over a period of more 

 than three years, 170 rabbits have been used for these experiments. The 

 rabbits were housed in individual cages and were fed a basal ration of 

 natural foods, modified slightly during the latter half of the work. The 

 basal rations were as follows: 



Crystalline cholesterol was mixed with the dry ration. Experience with 

 feeding 1 percent cholesterol for ten to twelve weeks proved that the 

 resulting injury was too severe to allow an inhibiting agent to show any 

 appreciable effect. Later work with 0.5 percent cholesterol, or a limited 

 amount of 1 percent, was more satisfactory. Preliminary trials with the 

 larger amounts yielded negative results so far as control of the condition 

 was concerned, but gave valuable information regarding the susceptibility 

 of rabbits to arterial change, and the necessity of more careful control of 

 sex, litter relationship, and food consumption than had been previously 

 used or reported by other investigators. 



The literature on this subject indicates that both organic and inorganic 

 forms of iodine may inhibit cholesterol injury, but no one seems to have 

 made a comparison of different forms of iodine under similar conditions. 

 Kelp, a seaweed containing large amounts of iodine, was selected as a 

 natural plant source of the chemical. It is not known just what the form 

 of iodine is in kelp. The value of kelp in the treatment of certain degen- 

 erative diseases has been recognized by some individuals in the medical 

 profession, but the reason for its apparent value is not known. 



In the experiments here reported, 17 percent of kelp was substituted 

 for an equal amount of bran, since both supply roughage in the diet. 

 Based on an average food intake of 100 grams per day, this amount of 

 kelp would supply 20 to 25 milligrams of iodine per day for each rabbit, 

 subject to some variation in the composition of the kelp and the food 

 intake of individual rabbits. The difiiculty of inducing the rabbits to eat 

 all of the kelp in the ration was never entirely overcome in spite of care 

 in grinding and mixing, and the use of a binder to keep the kelp well 

 mixed with the feed. In view of subsequent findings with the kelp ration, 

 these discrepancies tend to strengthen rather than to weaken the con- 

 clusions. 



Potassium iodide was chosen as the inorganic form of iodine to be used. 

 It was fed as such to the rabbits either in drinking water or mixed with 

 feed in amounts sufficient to furnish 25 milligrams of iodine daily for 



