NO. 3 COMPABATIVE HISTOLOGY OF FEMUR FOOTE 127 



LEFT FEMUR OF EQUUS CABALLUS. DOMESTIC HORSE. CR. MED. COLL. 



Pl. 16, Fig. 253. Syn. Tab. V I 



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". It has more Haversian systems than laminae. 

 The external circumferential lamellfe 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 lacunae are 

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

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

 proach the posterior wall. The lamina^ are well developed and are separated 

 by Haversian systems. Internal circumferential lamelhi? form a narrow ring 

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



Type II-III, C. 



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



PL. 16, Fig. 354. 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, brandling canaliculi. Between the 

 external laminae and internal circumferential lamellae 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 lacunae 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'. The laminae are separated by wide canals which frequently cross and 

 unite with otiier canals. Kach lamina is composed of laniciln' willi oval lacuna} 

 and bushy canaliculi. The innei- wall of the bone has (ihiiiiiic lainiiue. Internal 

 circumferential lamellae surround the medullary canal. 



Type II-III, C. 



