NO. 3 



COMPARATIVE HISTOLOGY OF FEMUR FOOTE 



195 



laminae with inter-laminar Haversian systems and canals. The lammas merge 

 together to some extent as they reach the anterior wall, hut are still evident in 

 that region. The Haversian systems of the horseshoe band are of the (la) and 

 (C) differentiations, the former predominating. Their locations between ad- 

 jacent lamina? produce irregular borders of the lamina;. In the anterior wall 

 the systems are all poorly developed, being little more than Haversian canals. 

 The lacunae of the lamella?, are long and narrow; of the laminae, somewhat oval. 



The central ring is narrow and composed of well developed Haversian sys- 

 tems in the outer, a wide band of lamella?, and Haversian systems in the anterior, 

 lamella? and Haversian systems in the inner wall, and Haversian systems in the 

 posterior ridge. No senile changes appear. The posterior ridge is composed 

 of Haversian systems and inter-Haversian lamella? with many oval lacuna?. The 

 internal circumferential lamellae form an irregular ring of varying widths around 

 the medullary canal. The bone is more than one-half lamina? and lamella?. 



Type I-II-III, la, C. 



LEFT FEMUR OF A WHITE MALE. NO. 99, CR. MED. COLL. 



Pl. 32, Fig. 404. Syn. Tab. X 



Antero-posterior diameter of bone, 30 mm. ; lateral, 27.5 mm. 

 Antero-posterior diameter of medullary canal, 14 mm. ; lateral, 10 mm. 

 The medullary canal is full. Medullary index, 20%. 



Structure. — Beginning on the outer side of the posterior ridge and extend- 

 ing around the lateral wall are coarse lamina 1 , interrupted by a few Haversian 

 systems of the (0) differentiation and by many of the (la) differentiation. As 

 the lamina? reach the anterior wall they merge into lamella?, which terminate in 

 the anterior inner wall, and are then completely displaced by well developed Ha- 

 versian systems. The lamina? again appear in the posterior wall. The lacunae, 

 are generally oval and their canaliculi straight. In the outer wall is a wide semi- 

 circular area of lamina?., which, with those of the external band, constitute the 

 whole wall. These laminae are also interrupted by Haversian systems similar 

 to those of the external band. 



The central ring is incomplete, since it is limited to a narrow portion of 

 the anterior, nearly the whole of the inner anterior and posterior wall. It is 

 composed of well developed Haversian systems without senile changes. 



The medullary canal is surrounded by laminae., interrupted by Haversian 

 systems of the (la) differentiation. The section is more than half lamella? and 

 lamina?. 



Type I-II-III, la, C. 



