NO. 3 



COMPARATIVE HISTOLOGY OF FEMUR FOOTE 



127 



LEFT FEMUR OF EQ.UUS CABALLUS. DOMESTIC HORSE. CR. MED. COLL. 



Pl. 16, Fig. 253. Syn. Tab. VI 



Antero-posterior diameter of bone, 57.5 mm. ; lateral, 41.5 mm. 

 Antero-posterior diameter of medullary canal, 32 mm. ; lateral, 22.5 mm. 

 The medullary canal is full. Medullary index, 43%. 



Structure. — The section is composed of rings of well developed Haversian 

 systems alternating with lamina 1 . It has more Haversian systems than laminae. 

 The external circumferential lamella? are fragmentary. The Haversian sys- 

 tems reach the external boundary, and in some places half-systems are present 

 with their Haversian canals directly underneath the periosteum. The Ha- 

 versian systems vary in diameter and are well developed. Their lacuna? are 

 long and their canaliculi are long and branching. Commencing in the outer 

 posterior region a few lamina 1 appear, which increase in number as they ap- 

 proach the posterior wall. The laminae are well developed and are separated 

 by Haversian systems. Internal circumferential lamella? form a narrow ring- 

 around the medullary canal and become cancellous in the posterior wall. 



Type II-III, C. 



RIGHT FEMUR OF OVIS. DOMESTIC SHEEP. CR. MED. COLL. 



Pl. 16, Pig. 254. Syn. Tab. VI 



Antero-posterior diameter of bone, 18 mm.; lateral, 14 mm. 

 Antero-posterior diameter of medullary canal, 10.7 mm. ; lateral, 7 mm. 

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



Structure. — External circumferential lamina? surround the section. The 

 lacunae are long and narrow with long, branching canaliculi. Between the 

 external lamina? and internal circumferential lamella 1 are small and large Ha- 

 versian systems, arranged in the form of a crescent and situated in the outer, 

 posterior, and inner lateral wall. The thickest portion of the crescent is in 

 the outer wall. The systems are, for the most part, small, close together, and 

 their Haversian canals frequently unite. They have few lacuna? and few bushy 

 canaliculi. The inner wall of the bone is composed almost entirely of laminae, 

 there being a few Haversian systems close to the internal circumferential la- 

 mella 1 . The lamina? are separated by wide canals which frequently cross and 

 mute with other canals. Each lamina is composed of lamella 1 with oval lacuna? 

 and bushy canaliculi. The inner wall of the bone has oblique lamina?. Internal 

 circumferential lamella? surround the medullary canal. 



Type II-III, C. 



