GROWTH OF CRANIUM 



83 



teeth, minus the mandible with lower teeth and minus the ear 

 bones. The mean weights are given in table 55. 



TABLE 55 



The mean weight in grams of the crania in each body weight group of the four series 

 of albino rats from Paris, London, Philadelphia, Vienna (based on table 4) Donald- 

 son ('IB a). Each weight group is based on six cases, three males and three females 



For the corresponding weights of the Norway crania see Table 84. 



3. Teeth. For the data on the growth of the incisor teeth (Ad- 

 dison and Appleton, '15), see chapter 3, p. 37-39. 



4. Blood. By means of a formula (19) based on his observa- 

 tions Chisolm ('11) was able to compute approximately the vol- 

 ume of the blood in rats of different body weights. Hatai (MS 

 '14) has added two formulas (19 a) (19 b) based on that of 

 Chisolm and giving results somewhat closer to the observations 

 when the determinations are made according to sex. 



These three formulas have been transformed in turn from vol- 

 ume to weight by using as a factor 1.056 — the specific gravity 

 of the blood — and three formulas for blood weight (20) (20 a) 

 (20 b) have been thus obtained. These last have been used to 

 compute the weight of the blood as given in table 70. Table 

 56 here given presents Chisolm's data on the other growth 

 changes in the blood. 



5. Fat. Boycott and Damant ('08, '08 a) have recorded the 

 proportion of fat in rats of both sexes and of increasing body 

 weights. 



The total fat was determined in healthy animals living under 

 ordinary laboratory conditions as to food. Xo details given. 

 The fat was estimated by Leathes' modification of Liebermann's 



