NO. 3 COMPAKATIVE HISTOLOGV OF FEMUR FOOTE 75 



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



Pl. 7, Fio. 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 lacume are long 

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

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

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

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



Type I-III, Ic. 



RIGHT FEMUR OF CATH.\RTES AURA. TURKEY-BUZZAKD. 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 lamellfe form a narrow 

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

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

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

 The lacunte 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 medullaiy 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 rotimdvs, is full of red marrow. No cancellous bone and no trabeculse 

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



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



