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HENRY II. DONALDSON 



of water, either on age or on body weight. The differences in the 

 graphs before puberty are the result of the method of construct- 

 ing the chart. It should be remembered, however, that age is 

 probably an important factor in modifying the percentage of 

 water, so that the use of the body weight as the basal datum is 

 open to question, except where the body weight is approximately 

 normal for the age. Such is the case, however, in our series. 



Chart 14 Percentage of water in the oven-dried cranium and in the vertebrae, 

 on body weight (albino rat) Table 16. 

 • Cranium, x Vertebrae. 



2. According to body weight 



Since body weight is a much more common datum than age, 

 it was felt that graphs for the percentage of water on body 

 weight would be particularly useful, and body weight has there- 

 fore been used exclusively for the remaining charts showing the 

 loss in the percentage of water. 



This percentage is somewhat different for the several parts 

 of the skeleton. Taking the body weight as a basis, we obtain 

 the series of values given in table 15 B, for the entire skeleton, 

 and the appendicular skeleton; in table 16 (chart 14) for the 

 cranium and the vertebrae, and in table 17 (chart 15) for the 

 humerus, the ulna plus radius, the fore foot, and table 18 (chart 

 16) for the femur, the tibia plus fibula, and the hind foot. 



If these several values are compared with one another, there 

 appear only slight differences between percentages of \\ ater in 



