NO. 3 COMPARATIVE HISTOLOGY OF FEMtU! FOOTE 63 



LEFT FEMUR OF AMAZONA ORATEIX. MEXICAN YELLOW-HEADED PARROT. NO. 3025, 



AMER. MUS. NAT. HIST. 



J'l,. r.. Fig. 81. Stn. Tab. Ill 



Antero-posterior diameter of bone, 4 mm. ; lateral, 3.5 mm. 



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



The medullary canal is full. Medullary index, 177%. 



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

 canaliculi, incompletely separated into dim laminsB by short, concentric canals 

 and interrupted by Haversian canals of the (la) differentiation. In the central 

 portion of the section, and extending nearly around it, is a concentric row of 

 Haversian systems of the (Ic) dift'erentiation. In the posterior wall, oval lacun;B 

 are crowded together along the medullary surface. 



Type II-III, la, Ic. 



RIGHT FEMUR OF TURDUS MIGRATORIUS. ROBIN. ("R. MED. COLL. 



Pl. 5, Fig. 82. Syn. Tab. Ill 



Antero-posterior diameter of bone, 2 mm.; lateral, 2 mm. 



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



The medullary canal is full. Medullary index, 129%. 



Structure. — The section is composed of concentric lamella; with oval and 

 long lacunae and straight and bushy canaliculi surrounding the medullary canal. 

 A concentric row of small Haversian systems of the (Ic) stage is found in the 

 central portion of the wall of the bone. A few canals cross the bone in different 

 directions. 



Type I-III, Ic. 



FEMUR OF PELECANUS ERYTHRORHYNCHUS. WHITE PELICAN. CR. MED. COLL. 



Pl. 5, Fig. 83. Syx. Tab. Ill 



Antero-posterior diameter of bone, 12 mm. ; lateral, 10 mm. 



Antero-posterior diameter of medullary canal, ; lateral, 0. 



The central ijortion of the bone is cancellous. Medullary index, 0. 



Structure. — The external circumferential lamellse form a narrow enclosing 

 ring. Underneath this is a central ring of Haversian systems of the (Ic) dif- 

 ferentiation with canals running at all angles. Beneath this is a narrow ring of 

 internal circumferential lamellfe from the inside of which is derived a cancellous 

 structure occupying the whole medullary region of the bone. The meshes are 

 filled with insoluble matter. A very small medullary canal is situated in the 

 posterior half of the section. 



Type T-IIT, Tc 



