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 

 laminfe 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. Tlie lacuniB are oval. 



The internal circumferential lamellae enclose the medullary canal. 



Type II-III, lb. 



* BIGHT 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. 



Anteroposterior diameter of medullary canal, 10.5 mm.; lateral, 8.5 mm. 



Medullary index, 23%. 



Structure. — The horseshoe l)and 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 lamellfe 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 l)one, 20 mm.; lateral, 21 mm. 



Antero-posterior diameter of nu'dullaiy cimal, 11 mm.; lateral, !) mm. 



Medullary index, 31%. 



The bone is adolescent. 



Structure. The section is suiToimded by extci'iial circumferenlial lamelhe. 



Many canals enter the section from the external sui-face. Here and there an 

 Haversian system appears. Tlie hicun:e are oval iiiid round. 



The central ring is composed of shoi-t lamella' and irregularly shaped 

 Haversian systems which are still undeveloped. Tlu'ir lacuuiv are oval and 

 round. 



