NO. 3 



COMPARATIVE HISTOLOGY OF FEMUR EOOTE 



133 



The posterior wall is composed entirely of Haversian systems of the (C) 

 differentiation. 



Type II-III, C. 



LEFT FEMUR OF URSUS MARITIMUS. POLAR BEAR. NO. 35085, AMER. MUS. NAT. HIST. 



Pl. 17, Pig. 265. Syn. Tab. VII 



Antero-posterior diameter of hone, 31 mm. ; lateral, 38 mm. 

 Antero-posterior diameter of medullary canal, 18 mm.; lateral, 22 mm. 

 The medullary canal is full. Medullary index, 51%. 



Structure. — The section has a rather peculiar shape. With the exception 

 of the posterior ridge it is surrounded by laminae, which, in the anterior wall, 

 merge into lamellae and are interrupted by Haversian systems. The central ring 

 is composed of concentric rows of well developed Haversian systems alternat- 

 ing with laminae, excepting in the posterior ridge which is all Haversian systems. 



Internal circumferential lamellae form a narrow ring around the medullary 

 canal. The bone is more highly differentiated than the femur of the black bear. 



Type II-III, C. 



RIGHT FEMUR OF BUBALIS JACKSONI. HARTEBEEST. NO. 37815, AMER. MUS. NAT. HIST. 



Pl. 17, Fig. 266. Syn. Tab. VII 



Antero-posterior diameter of bone, 32.5 mm. ; lateral, 30 mm. 

 Antero-posterior diameter of medullary canal, 17 mm. ; lateral, 16 mm. 

 The medullary canal is full. Medullary index, 39%. 



Structure. — The section is composed mostly of laminae. Around the bone 

 is a wide horseshoe band of laminae, interrupted by Haversian systems. The 

 band forms the whole of the outer and anterior walls. Underneath the band in 

 the inner wall is a narrow crescent of well developed Haversian systems. The 

 posterior wall is composed of Haversian systems and short lamina?, between 

 which are several vascular canals. A narrow ring of internal circumferential 

 lamellae, slightly wider in the inner wall, surrounds the medullary canal. The 

 lacunae are long and oval. 



Type II-III, C. 



LEFT FEMUR OF PHACOCHCERUS AFRICANUS. WARTHOG. NO. 27762, 



AMER. MUS. NAT. HIST. 



Pl. 17, Fig. 267. Syn. Tab. VII 



Antero-posterior diameter of hone, 24 mm. ; lateral, 20.5 mm. 

 Antero-posterior diameter of medullary canal, 14 mm.; lateral, 12 mm. 

 The medullary canal is full. Medullary index, 52%. 



