NO. 3 



COMPARATIVE HISTOLOGY OF FEMUK FOOTE 



139 



RIGHT FEMUR OF A BULL, DOG ( NOT A PURE BLOOD). NO. 292, CR. MED. COLL. 



Pl. 19, Fig. 279£. Syn. Tab. VII 



Antero-posterior diameter of bone, 14.5 mm.; lateral, 12.5 mm. 

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

 The medullary canal is full. Medullary index, 109%. 



Structure. — The section is composed of a horseshoe of laminae and lamella 1 , 

 separated into two bands by a central band of Haversian systems. The lamina 1 

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

 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 1 . 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 (NOT A PURE BLOOD). NO. 201, CR. MED. COLL. 



Pl. 19, Pig. 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 lamina? which 

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

 widen into circular areas at intervals. The lacunas 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 ppsterior ridge is almost 

 entirely composed of Haversian systems. The internal circumferential lamella; 

 form a narrow ring around the medullary canal. 



Type H ill, C. 



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



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



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

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

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



Structure. — The section is composed of a horseshoe band of lamellae 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 band of Haversian systems. The lamellar bands are frequently 



