BONES 



49 



affect total length of the forelimb. The slightly delayed fusion 

 of both proximal and distal ends of the fibula, as compared 

 with the tibia, may explain the decided bowing of the fibula 

 from the tibia. 



Skull measiiremerits. For data on the growth of the entire 

 skeleton see Chapter 6. 



TABLE 15 a 

 {A. B. Dawson, MS. '24). Age and sequence of fusion of the epipJujses in the 



long bones 



Skull measurements have been made by Hatai ('07 c). 

 following description is extracted from his paper. 



The 



For this study 53 male and 51 female skulls of mature Albinos (rats 

 more than 150 daj^s old) were measured. These skulls had been care- 

 fully cleaned and dried at room temperature. The following measure- 

 ments were made with vernier calipers: 1) the length of the entire 

 skull; 2) the fronto-occipital length; 3) the zygomatic width; 4) the 

 length of the nasal bone; 5) the height of the skull; 6) the width of 

 the cranium or the squamosal distance. In every case the maximum 

 length alone was recorded in millimeters. 



The horizontal straight line joining the tip of the nasal bone to the 

 end of the occipital bone is called the length of the entire skull. This 

 however is not exactly equal to the sum of the length of the nasal bone 

 and that of the fronto-occipital. 



The fronto-occipital length was determined in the following way: 

 Since the length measured with the calipers from the tip of the nasal 



