NO. 3 



COMPARATIVE HISTOLOGY OF FEMUR- — FOOTE 



175 



Structure. — With the exception of the posterior ridge the section is sur- 

 rounded by a band of laminae and Haversian systems. In the outer wall the 

 laminae are perforated by small longitudinal canals. 



The central ring forms nearly all of the inner wall and little or none of 

 the outer wall. It is composed of crude Haversian systems. The systems are 

 irregular in shape with oval lacunae. 



The posterior ridge has blended with the lateral walls and is composed of 

 crude Haversian systems. The lacunae are oval. 



The internal circumferential lamellae enclose the medullary canal. 



Type II-III, lb. 



* RIGHT FEMUR OF AN ADULT PACHACAMAC INDIAN. NO. 10, U. S. NAT. MUS. 



Syn. Tab. IX 



Antero-posterior diameter of bone, 21.5 mm. ; lateral, 20 mm. 

 Antero-posterior diameter of medullary canal, 10.5 mm. ; lateral, 8.5 mm. 

 Medullary index, 23%. 



Structure. — The horseshoe band around the section is evident. It is com- 

 posed of a lamellar background, most pronounced in the inner and anterior wall, 

 interrupted by numerous irregularly shaped Haversian systems. 



The central ring is composed of Haversian systems. 



The medullary canal is enclosed by internal circumferential lamellae which 

 expand into a crescent in the inner wall. It is crossed by radiating canals and 

 interrupted by scattering Haversian systems. The lacunae are oval. 



Type I-III, la, C. 



* LEFT FEMUR OF A PACHACAMAC INDIAN. NO. 5, U. S. NAT. MUS. 



Syn. Tab. IX 



Antero-posterior diameter of bone, 20 mm. ; lateral, 21 mm. 

 Antero-posterior diameter of medullary canal, 11 mm.; lateral, 9 mm. 

 Medullary index, 31%. 

 The bone is adolescent. 



Structure. — The section is surrounded by external circumferential lamellae. 

 Many canals enter the section from the external surface. Here and there an 

 Haversian system appears. The lacunae are oval and round. 



The central ring is composed of short lamella 1 and irregularly shaped 

 Haversian systems which are still undeveloped. Their lacunae arc oval and 

 round. 



