NO. 3 COMPARATIVE HISTOLOGV OF FEMUR FOOTE 41 



RIGHT FEMUR OF CHOROPHILUS FERIARUM. NO. E 52 47, U. S. NAT. MUS. 



Pl. 2, Pici. JT. Stn. Tab. I 



Antero-posterior diameter of bone, 0.5 mm. ; lateral, 0.4 mm. 



Antero-posterior diameter of medullary canal, 0.2 mm. ; lateral, 0.2 mm. 



The medullary canal is full. Medullary index, 24%. 



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

 straight canaliculi, divided into wide external and narrow internal rings. The 

 internal ring forms the internal circumferential lamellae. Twofold division. 



Type I. 



RIGHT FEJIUR OF ACRIS GRYLLUS. U. S. NAT. :MUS. 



Pl. 2, Fig. 18. Syx. Tab. I 



Antero-posterior diameter of bone, 0.5 mm.; lateral, 0.3 mm. 



Antero-posterior diameter of medullary canal, 0.2 mm.; lateral, 0.1 mm. 



The medullary canal is full. Medullary index, 16%. 



Striicture.- — The section is composed of lamellae with oval lacunai and 

 straight canaliculi, divided into wide external and narrow internal rings. The 

 internal ring forms the internal circumfei-ential lamellae. Twofold division. 



Type I. 



RIGHT FEMUR OF RAN A CATESBIANA. BULL FROG. AMER. MUS. NAT. HIST. 



Pl. 2, Fig. 19. Sy\. Tab. I 



Antero-posterior diameter of bone, 2.5 mm.; lateral, 2.5 mm. 



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



The medullary canal is full. Medullary index, 56%. 



Structure. — The section is composed of lamellae with round, oval, and long 

 lacunjE and straight, long, thickly set canaliculi, arranged concentrically around 

 the medullary canal. The bone is uniform. 



Type I. 



RIGHT FEMUR OF RANA PALUSTRIS. XO. F 52 22, U. S. NAT. MUS. 



Pl. 2, Fig. 20. Syv. Tab. I 



Antero-posterior diameter of bone, 1 mm,; lalci-al, O.S mm. 



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



The medullary canal is full. Medullary index. 44%. 



Structure. — The section is composed of concentric lamellte witli round and 

 oval lacuna} and bushy canaliculi, separated into two concentric rings. The 

 positions of the lacunae and canaliculi give a radiating effect. The internal 

 ring forms the internal circumferential lamellae. Twofold division. 



Type I. 



