K04 Self-Selection of Diets 



metabolism of fat. Mannering, Lipton and Elvehjem'' have recently arrived 

 at this conclusion on the basis of their biochemical studies. Our results have 

 also indicated that protein metabolism is largely dependent on the vitamin B 

 complex. 



9. The self-selection technique may be used to bio-assay hormone and vita- 

 min preparations. Thus, the increased calcium lactate appetite of parathy- 

 roidectomized rats has been used to bio-assay vitamins which affect calcium 

 metabolism. It was found that the calcium lactate intake could be reduced to 

 approximately its normal level by 3,730 irradiated vitamin D units per kilo- 

 gram body weight of vitamin D^ (crystalline); 8,880 units of irradiated ergos- 

 terol; 3,380 units of vitamin D3 (crystalline); or by 3,770 units of irradiated 

 cholesterol. Daily doses of dihydrotachysterol (A.T. 10) in minute amounts, 

 35 jLig. suffice to decrease the daily calcium lactate intake to its normal level. 

 Parathyroid extract injected daily did not reduce the calcium lactate intake 

 to its normal level until doses of 100 units per day were administered. This 

 dosage was definitely toxic (Richter and Birmingham"). Similar assays have 

 been made on the sodium regulatory functions of desoxycorticosterone using 

 the sodium chloride appetite of adrenalectomized rats as a measure. 



10. The maintenance of the total caloric intake at its normal level prevents 

 the appearance of deficiency and other disturbances. It was found that when 

 rats are forced to consume added calories with their drinking water they will 

 reduce the caloric intake from their food in direct proportion to that taken 

 from the other source. Thus, rats given a 16 per cent solution of alcohol as the 

 sole source of water reduced their food intake directly in proportion to the 

 caloric value of the ingested alcohol. This meant that the total caloric intake 

 remained the same. That this actually was a beneficial selection is shown by 

 the fact that rats which have been forced for over one hundred days to take 

 50 per cent of their total caloric intake in the form of alcohol did not develop 

 any deficiency symptoms. It may be that in human beings similar effects from 

 the use of alcohol depend on the fact that the caloric intake from the food 

 added to that from the alcohol gives a total caloric intake which far surpasses 

 the normal caloric requirements. If forced to take sugar in the same way, rats 

 will reduce their food intake so that the total does not surpass the normal 

 level (Richter'). 



11. Solutions preferred in ayiy concentration to ivater by the rats are apt to 

 have nutritional value, while those which are not preferred to water in any 

 concentration are apt to have no nutritional value or to be toxic. Thus, rats 

 were found to prefer solutions of the following substances to water: dextrose, 

 maltose, levulose, sucrose, galactose, sodium chloride, potassium chloride, cal- 

 cium lactate, alcohol— all of which are known to have a nutritional value. On 

 the other hand, they were found to prefer water to solutions of the following 

 substances: mercuric chloride, morphine sulphate, arsenic trioxide, phenyl- 

 thiocarbamide— all of which are known to be poisonous (Richter and Camp- 

 bell). 



