NO. 3 



COMPARATIVE HISTOLOGY OF FEMUR FOOTE 



51 



posterior wall a little cancellous bone appears. The bone shows an early dif- 

 ferentiation by its traces of laminae and Haversian canals. 

 Type I-III, la. 



RIGHT FEMUR OF AMPHIBOLUKUS BARBATUS. (AUSTRALIA.) 

 AMER. MUS. NAT. HIST. 



Pl. 3, Pig. 47. Syn. Tab. II 



Antero-posterior diameter of bone, 3 mm. ; lateral, 4 mm. 

 Antero-posterior diameter of medullary canal, 1.5 mm.; lateral, 2.5 mm. 

 The medullary canal is full. Medullary index, 49%. 



Structure. — The section is composed of concentric lamellae with long and 

 oval lacunae and long, straight canaliculi surrounding the medullary canal. No 

 differentiation of structure is present. A large, vascular canal appears in the 

 inner wall. The section is uniform. 



Type I. 



LEFT FEMUR OF VARAN US ARENARIUS. AMER. MUS. NAT. HIST. 



Pl. 3, Pig. 48. Syn. Tab. II 



Antero-posterior diameter of bone, 4.5 mm. ; lateral, 3 mm. 

 Antero-posterior diameter of medullary canal, 3 mm. ; lateral, 2 mm. 

 The medullary canal is full. Medullary index, 45%. 



Structure. — The section is composed of concentric lamellae with oval lacunae 

 and bushy canaliculi arranged around the medullary canal. Many small canals 

 traverse the walls of the bone radially from the medullary canal outward and 

 from the external surface inward. There is very little differentiation of struc- 

 ture. The section is uniform. 



Type I. 



RIGHT FEMUR OF VARANUS NUCHALIS. MONITOR. AMER. MUS. NAT. HIST. 



Pl. 3, Pig. 49. Syn. Tab. II 



Antero-posterior diameter of bone, 4.5 mm.; lateral, 3.5 mm. 

 Antero-posterior diameter of medullary canal, 3 mm. ; lateral, 2.5 mm. 

 The medullary canal is full. Medullary index, 88%. 



Structure. — With the exception of a small area of lamellae along the medul- 

 lary surface of the posterior wall, the section is composed of concentric lamella' 

 with oval lacunae and bushy canaliculi, interrupted by a large number of short, 

 radiating canals around which are clear areas of bone substance. In the pos- 



