to2 Sel£-Selectioii of Diets 



containers, using dextrose or sucrose as a source of carbohydrate, casein 

 (autoclaved and purified) for protein, and olive oil for fat; crystalline thiamin 

 chloride, riboflavin, nicotinic acid, pyridoxin, pantothenic acid, and choline 

 chloride as representatives of the vitamin B complex; cod liver oil for vitamins 

 A and D; and solutions of sodium phosphate, sodium chloride, calcium lactate, 

 magnesium chloride, and potassium chloride for the minerals. Some of these 

 rats gi-ew at a normal rate and showed regular vaginal smear cycles (Richter 

 and Hawkes^^. 



2. Rats kept on a vitamin-deficient diet will seek vitamins or substances 

 which help to replace vitamins. Thus, rats kept on this self-selection diet with- 

 out any of the vitamin B factors will eat large amounts of yeast or liver when 

 these substances are offered to them and as a result quickly correct their 

 deficiency. If not given access to a source of the B complex the rats will eat 

 almost no carbohydrate, but take large amounts of fat, which apparently can 

 be at least partially metabolized under these circumstances (Richter, Holt, 

 Barelare and Hawkes^*). 



3. The appetite for carbohydrate and fat always shows an inverse relation- 

 ship. When rats have a marked craving for fat, they refuse carbohydrate and 

 vice versa. Many instances of this relationship have been observed. Thus, 

 vitamin B-deficient rats stop eating carbohydrate and eat large amounts of 

 fats. Almost at once after they have access to vitamin B in the form of yeast, 

 they reverse their appetites, stop eating fat and eat large amounts of carbo- 

 hydrate. Rats made diabetic by pancreatectomy stop eating carbohydrate and 

 start eating fat, then when treated with insulin reverse their appetite. After 

 ligature of the bile duct, rats stop eating fat and start eating carbohydrate. 

 Spontaneous changes in appetite for fat are always accompanied by inverse 

 changes in the carbohydrate appetite. 



4. The appetites for carbohydrate, fat, and protein, are dependetit to a large 

 extent on the amount of the various components of the vitamin B complex 

 present in the diet. By varying the combination of vitamin B components 

 made accessible to the rats we are able almost at will to make a rat manifest 

 a marked appetite or a marked aversion for either carbohydrate, fat, or pro- 

 tein. In the absence of all vitamin B, rats eat large amounts of fat, little or no 

 carbohydrate, and no protein. When thiamin chloride is made available as 

 the sole representative of the vitamin B complex they eat carbohydrate, little 

 fat, and still completely avoid protein. Progressively, as the other components 

 are made available they eat more carbohydrate, less fat, more protein. When 

 thiamin chloride, riboflavin, nicotinic acid, pyridoxin, pantothenic acid, 

 choline chloride, and biotin are made available they thrive on a diet of very 

 little fat, high carbohydrate, and moderately high protein. 



5. Bulk apparently is not necessary. On the self-selection diets in which only 

 purified substances were used, bulk was reduced to a minimum. The animals 

 passed only a few small feces. The good health of the rats showed that bulk 

 was unnecessary. 



