NO. 3 COMPARATIVE HISTOLOGV OF FEMUR FOOTE 139 



RIGHT FEMUR OF A BX'LL DOG (nOT A PURE BLOOD). NO. 292, CK. MED. COLL. 



Pl. 19. Fig. 2794. Stx. Tab. VII 



Aiitero-posterior dianieter of bone, 14.5 mm.; lateral, 12.5 mm. 



Antero-posterior diameter of medullary canal, 10.5 nun.; lateral. 9 mm. 



The medullar)' canal is full. Medullary index, 109'/;;. 



Structure. — The section is composed of a horseshoe of lamina' and lamella?, 

 separated into two bauds by a central band of Haversian systems. Tlie lamina' 

 constitute the whole of the inner wall, and as they reach the anterior wall thej- 

 become lamellae, which are then separated into external and internal bands by a 

 central band of Haversian systems. The three bands, external lamellar, central 

 Haversian system, and internal lamellar form the outer wall. The internal 

 lamellae are frequently crossed by radiating canals. The posterior ridge is com- 

 posed of Haversian systems with comparatively few lacuna'. Their bone sub- 

 .stance is in excess of that usually seen. In the anterior wall near the medul- 

 lary canal are four quite large openings. 



Type I-II-III, C. 



LEFT FEMUR OF A SHEPHERD DOG (XOT A Fl'RE BLOOD). NO. 201, CK. .MED. COLL. 



Pl. 19, Fig. 280. Syn. Tab. VII 



Antero-posterior diameter of bone, 11 mm.; lateral, 10.5 mm. 



Antero-posterior diameter of medullary canal, 6.5 mm. ; lateral, 5.5 mm. 



The medullary canal is full. Medullary index, 45%. 



Structure. — The section is surrounded by a horseshoe band of laminae which 

 constitutes the principal part of the bone. Between the lamiufe are canals which 

 widen into circular areas at intervals. The lacuna? are oval and long. The cen- 

 tral ring is reduced to a long, narrow crescent of Haversian systems extending 

 around the anterior, outer, and posterior wall. The posterior ridge is almost 

 entirely composed of Haversian systems. The internal circumferential lamellae 

 form a narrow ring around the medullary canal. 



TjT)e II-III, C. 



RIGHT FEMUR OF A DOG. NO. 291, CK. MED. COLL. 



Pl. 19. Fig. 280^ Syn. Tab. VII 



Antero-posterior diameter of bone, 16 mm.; lateral, 17 nun. 



Antero-posterior diameter of medullary canal, 11 nnn. ; lateral. 10 mm. 



The medullary canal is full. Medullary index, 68%. 



Structure. — The section is composed of a horseshoe band of lamelhe and 

 laminae, interrupted by Haversian systems of the (la) differentiation. In the 

 outer wall the lamellae are separated into two nearly equal concentric bands by 

 a middle l)aii(l of Haversian systems. The lamellar bands are frequently 



