NO. 3 



COMPARATIVE HISTOLOGY OF FEMUR FOOTE 



75 



LEFT FEMUR OF INOCOTIS PAPILLOSUS. IBIS. NO. 3178, AMER. MUS. NAT. HIST. 



Pl. 7, Fig. 111. Syn. Tab. Ill 



Antero-posterior diameter of bone, 7 mm. ; lateral, 6.5 mm. 

 Antero-posterior diameter of medullary canal, 6 mm. ; lateral, 5.5 mm. 

 Medullary index, 264%. 



Structure. — The section shows the three divisions. External circumfer- 

 ential lamellae form a narrow ring around the section. Their lacunae are long 

 and narrow. Underneath this ring is a wide central ring of lamellae, Haversian 

 systems, and canals. The lamellae have oval lacunae and bushy canaliculi. The 

 Haversian systems are of the (Ic) stage of development. Around the medullary 

 canal is a ring of lamellae with long and narrow lacunae. 



Type I-III, Ic. 



RIGHT FEMUR OF CATHARTES AURA. TURKEY-BUZZARD. NO. 70, CR. MED. COLL. 



Pl. 7, Fig. 112. Syn. Tab. Ill 



Antero-posterior diameter of bone, 9.5 mm. ; lateral, 8 mm. 



Antero-posterior diameter of medullary canal, 7.5 mm. ; lateral, 7 mm. 



The medullary canal is empty. Medullary index, 219%. 



Structure. — The walls are very thin and hard. The usual three structural 

 divisions are present. The external circumferential lamellae form a narrow 

 ring around the section excepting in the posterior ridge where a few tendon 

 insertions displace them. Their lacunae are long, narrow, and well developed. 

 The central ring is composed of Haversian systems of the (Ic) differentiation. 

 The lacunae are some distance apart and their canaliculi are rather infrequent. 

 The ring is crossed at all angles by canals. The internal circumferential 

 lamellae constitute a narrow ring around the medullary canal. Their lacunae 

 are well developed. 



Type I-III, Ic. 



IX. MAMMALS— BATS 

 Fifty-five femora were examined. 



General Character of the Femur 



The prevailing shape of the femur is elliptical. Several are round, and a 

 few are plano-convex. The medullary canals are all full of marrow and one, 

 Desmodus rotundus, is full of red marrow. No cancellous bone and no trabecular 

 are found. The medullary surfaces are smooth or very slightly corrugated. 



The medullary index varies from 12% to 178% with an average of 48.6%. 



