COXSEHVATIOX OF .SKELETAL CALCHM ATOMS TllKOUCll LITE 22:i 



EXPERIMENTAL 



In view of the dill icult i(>s in r(>pluc'ing all food ciUciuni hy ialjollod oalciuin. 

 wo added the labelled caleium as CaCl^ (150 mgm. per liter) to tlu^ drinking wa1(M-. 

 on the assumption that the quantity of water drunk by tlie nions(>, kept at (con- 

 stant teni])eratuie, is about proportional to the intake of food which consisted 

 of standard cakes. We started to administer two to ten weeks before parturition 

 to 20—30 gm mice the labelled CaClg nnd continued administration of such 

 drinlving water till weaning. Then, the growing mice were given labelled drinking 

 water until they were outgrown. From that date (when the mice were aljoul 

 100 days old), administration of *^Ca was discontinued. The offspring were killed 

 at different times, and the radioactivity of the ash of their skeletons was compared- 

 20 mg. of bone ash were placed under the Geiger counter, and the total activity 

 of the skeleton was calculated fiom the measured activity and the total ash weight. 

 In other experiments, the radioactivity of the total body ash samples was com- 

 pared. 



The ratio of the activity of 20 mgm of Ijone asli of outgiown and of newborn 

 mice is not a correct measure of their relative *^Ca content. The calcium content 

 of the ash of the newborn being appreciably lower than that of the adult, the 

 backseat tering of the j^-rays emitted by the ^^Ca of the first mentioned samples 

 will be lower, furthermore the consistency of the samples and, thus, the distance 

 of the sample from "the counter window may slightly differ. By measuring once 

 the activity of a 20 mgm sample of the bone ash of newborn mice, and then that 

 of a small known aliquot of this sample brought up to 20 mgm through addition 

 of inactive bone ash of an adult mouse, wt arrive at the result that the activity 

 measured of the ash of the newborn mouse has to be multiplied by 1.05 in order 

 to make it comparable with the activity of the bone ash of adult mice. 



In other experiments, new-boin mice were shifted from their active mothers 

 to inactive mothers shortly after birth; determinations were made of the percent- 

 age of maternal labelled calcium taken up by the offspring after birth and the 

 rate of loss of these calcium atoms during growth and later. 



The ^^Ca activity of the mice remained below 0.05 ^C per gm and, in most 

 cases, it was very appreciably less. Simmons and assoc.^^-^ observed the effects 

 of radiation produeed in mice during 108 weeks. When a dose of 0.034 juV per gm wa , 

 administeied, they could not find anaemia; when the dose was laised to 0.068 juC 



Table 2. — Composition of Cakes Fed to orR Mice ("Gard-kred")* 



100 gm cakes (.■outain 



Water 



Ash 



Proteins (.l.T >( N) 

 Carbohydrates . . . 



Ca 



P 



Fe 



Combustion value (calculated according to Rubner) .... 400 cal. 



* In Sweden, mice and rats are fed almost exclusively on these cakes, the exact composition of wliicli 

 was hitherto unknown. The author is much indebted to Professor E. BRrNU's and Mrs. EsTHKR SIHLBOM 

 wlio most kindly made the analysis of these cakes at Statens Institut for Kolkhiilsan. 



