GROWTH OF THE SKELETON 



309 



the case of each skeleton, together with the total number of 

 separate bones in each group as these were prepared. 



If we take the bones more in detail the following numbers 

 appear: 



There are twenty claws — also not weighed with the skeleton. 

 In the case of forty skeletons the percentage of the weight of 

 the room-dried claws on the weight of the fresh skeleton gives 

 the following values : 



TABLE 33 

 Weight of claws 



small ossicles which represent the chevron bones. About twenty-six of these 

 pairs are found in the tail of the full-grown albino rat. These chevron ossicles 

 were not counted in enumerating the bones, nor were they weighed with the 

 vertebrae. 



5 There are fourteen small sesamoid bones in each fore foot and fourteen small 

 sesamoid bones in each hind foot. These were not weighed. 



6 The tibia and fibula are counted separately, but have been weighed together, 

 because at twenty days of age, or sometimes earlier, the fibula unites with the 

 tibia, and after that age it becomes increasingly difficult to separate these two 

 bones. 



