6o 



Scientific Proceedings (117). 



normalities, whereas 0.2 per cent, furnished sufficient vitamine A 

 to keep the animal alive for 3 or more months. The addition of 

 0.5 gram of butter fat per day did not lessen the abnormalities. In 

 order to determine the growth of the bones x-ray plates were made 

 by photographing a large number of animals on the same plate and 

 comparing the density of the shadows of the bones. In addition, 

 determinations of calcium intake and output and calculations 

 of the calcium retention were made. Considerable individual 

 variation was found, but when long metabolism periods (about a 

 week) were used and all our animals with abnormal bones were 

 averaged we found that rats which were weaned and placed on the 

 diet at the age of twenty-one days and left on this diet at least 

 three days before commencing the metabolism study showed a re- 

 tention of 2.7 milligrams of calcium per rat per day for the first 

 two weeks, 1.7 for the third week and 1.5 for the fourth week. 

 In some individual rats shortly before death we obtained negative 

 calcium balances. It would indicate, therefore, that the dis- 

 turbance of calcium metabolism is increasing in severity from the 

 first to the fourth week. We do not know the average calcium 

 retention of the normal rat but we assume that it is close to 5 

 milligrams per day for the ages corresponding to our rats. This 

 is based on calcium content of whole rats. It seems probable, 

 therefore, that calcium retention can be used throughout the 

 course of the disorder as an index of the severity of the disease, 

 provided adequate methods are used to determine the calcium 

 retention. In order to avoid errors due to transfer of the excreta 

 we have made round cages with quarter-inch-mesh wire screen 

 bottoms that sit in silica dishes six inches in diameter and have 

 two bird-feed cups attached, one for water and one for food. 

 Any food spilled from the container into the dish does not cause 

 an error because it does not affect the difference between the 

 intake and the outgo of calcium. At the end of the metabolism 

 period the cage is lifted from the dish and the excreta ashed in 

 the dish. In order to "separate the calcium from the dissolved 

 ash as calcium oxalate we have used a bromphenol blue as an 

 indicator for hydrogen ion concentration. If the solution which is 

 acid is neutralized until it reaches P H = 4 the calcium oxalate will 

 not be appreciably soluble and yet no calcium will precipitate as 



