NO. 3 



COMPARATIVE HISTOLOGY OF FEMUR FOOTE 



173 



The internal circumferential lamella? enclose the medullary canal. It is a 

 fairly wide band in the lateral walls. The lacuna? of the section are generally 

 oval. 



Type I-II-III, la, C. 



* RIGHT FEMUR OF AN ADULT PACHACAMAC INDIAN. NO. 14, U. S. NAT. MUS. 



Syn. Tab. IX 



Antero-posterior diameter of bone, 24 mm. ; lateral, 21 mm. 



Antero posterior diameter of medullar}'' canal, 14 mm. ; lateral, 10 mm. 



Medullary index, 38%. 



Structure. — Slight evidences of the horseshoe band are present. The la- 

 mella? are most pronounced in the anterior wall where they form a fairly wide 

 band. In the lateral wall the lamella? are separated into lamina?, between which 

 are small Haversian systems of the (la) differentiation. 



The central ring is composed of Haversian systems. In the outer and inner 

 wall inter-Haversian lamella? are present. The internal circumferential lamella? 

 enclose the medullary canal. In the outer wall they expand into a wide crescent, 

 which is broken into irregularly shaped fragments by interrupting Haversian 

 systems. The lacuna? are long, narrow, and oval. 



Type I-II-III, la, C. 



* RIGHT FEMUR OF A PACHACAMAC INDIAN. NO. 13, U. S. NAT. MUS. 



Syn. Tab. IX 



Antero-posterior diameter of bone, 16 mm. ; lateral, 15 mm. 

 Antero-posterior diameter of medullary canal, 8 mm. ; lateral, 7 mm. 

 Medullary index, 30%. 



Structure. — The section is surrounded, with the exception of the posterior 

 ridge, by a horseshoe band of laminae in the outer and anterior wall and of 

 Haversian systems of the (la) differentiation in the inner wall. The lamina 1 

 are frequently perforated by small canals and in the anterior wall they sud- 

 denly widen and occupy the whole wall. As they approach the inner wall they 

 bend around the inner anterior angle and are then displaced by very crude 

 Haversian systems. 



The central ring is reduced to a crescent in the outer wall. It is composed 

 of crude Haversian systems and lamella 1 . 



The posterior ridge is not distinguishable from the lateral wall and con- 

 sists of Haversian systems and short lamina? having a direction parallel with 

 the external surface. 



