NO. 3 



COMPARATIVE HISTOLOGY OF FEMUR FOOTE 



37 



and most complete. They are all of the first type, though of different develop- 

 ments. In figure 1 the radiating canals with poorly developed intervening 

 lamella? indicate an early stage of development. In figure 2 more than half of 

 the canals have disappeared and better developed lamella? are formed. In 

 figure 3 all of the canals have disappeared and the whole bone is composed of 

 concentric lamella?. 

 Type I. 



RIGHT FEMUR OF RANA CATESBIANA (SMALL.) . FOURTH BULL FROG. CR. MED. COLL. 



Pl. 1, Fig. 4. Syn. Tab. I 



Antero-posterior diameter of bone, 1 mm. ; lateral, 1.5 mm. 

 Antero-posterior diameter of medullary canal, 0.5 mm. ; lateral, 0.6 mm. 

 Medullary index, 24%. 



Structure. — The section is composed of concentric lamella? with long lacuna 1 

 and long, straight canaliculi surrounding the medullary canal. The section has 

 a uniform structure. 



Type I. 



fractured and repaired femur of a frog. cr. med. coll. 



Pl. 1, Fig. 5. Syn. Tab. 1 



Antero-posterior diameter of bone, 1.5 mm.; lateral, 1.7 mm. 

 Antero-posterior diameter of medullary canal, 0.6 mm. ; lateral, 0.7 mm. 

 The medullary canal is full. Medullary index, 20%. 



Structure. — One of the femora had heen fractured about the middle of the 

 shaft. The ends of the bone had slipped by each other, and new bone had 

 formed around the fragments. In section (fig. 5) which was taken from the 

 middle of the new bone, two cuts of the femur appear situated eccentrically. 

 The sections are composed of concentric lamella? with oval and straight lacunae 

 surrounding the medullary canals. 



The upper fragment, H, proximal, shows cell growths bursting through the 

 wall of the bone (pl. 1, fig. 5, A, B). In the lower fragment, D, distal, no cell 

 outbursts appear. 



Around the two fragments and extending between them is a formation of 

 cancellous or channeled bone which is the new bone of repair. Some of the 

 meshes of this bone are occupied by newly deposited lamella?, and resemble 

 Haversian systems, although there are no Haversian systems or cancellous 

 bone in the femur of the frog (pl. 1, fig. 5 0, E). This fact suggests a genetic 

 relationship between cancellous bone and Haversian systems. 



Type I. 



