426 EFFECTS OF RADIUM RADIATIONS ON WHITE MICE 



adjusted so that the tube was either directly over the central dorsal 

 region or over the head of the animal. The time of exposure was 

 always 5 minutes. The amounts of emanation employed and the 

 number of treatments given on successive days are shown in Table I. 



To identify the controls from the radiated mice in the same litter 

 a small piece of tail was clipped off from the specimens of one group. 

 The mice of each group were weighed together for the first time within 

 12 hours of the time of birth, and then every 24 hours until the 21st 

 day, when the young were suckled. From this time on the mice were 

 weighed individually about once a week. For any group the average 

 weight for one mouse was calculated. A careful record was kept of 

 the physical condition, body weight, and hair development for the 

 different mice; also the time when they opened their eyes or reached 

 sexual maturity, and the duration of life. 



The biological effect of radium radiations is related to the amount 

 of radiant energy absorbed by the tissue. This depends on various 

 factors, of which the quality of radiation used and the distance of 

 application are the most important ones. At the present time there 

 is no satisfactory unit in which to express the dose of radiation adminis- 

 tered. In these experiments radium emanation enclosed in capillary 

 glass tubes of a definite size was used as the source. The quality of the 

 radiation employed, mainly /3-rays, therefore, was always the same, 

 and the animal was placed at a distance of 2 cm. from the emanation 

 tube for every treatment. Under these conditions the dose depends 

 only on the amount of emanation in the tube and the duration of the 

 application. The former is given in millicuries and the latter can be 

 expressed in hours ; the product of the two (millicurie hours) in this case 

 may be taken to represent the relative doses. It should be noted in 

 this connection that in each case the millicurie hour dose appearing 

 in Table I is the total administered during the whole period of treat- 

 ment in fractional daily doses. 



The typical effects of different doses are shown graphically in 

 Fig. 2. Here the body weights of the radiated mice and their respec- 

 tive controls are given for a period of 8 weeks, this being the time 

 during which the maximum radium reaction is likely to occur. It 

 will be seen that a dose of 2.4 millicurie hours, fractionally applied, 

 in the manner previously described, accelerated the growth of the mice. 



