NO. 6 COMPARATIVE HISTOLOGY OF FEMITR FOO'lE 111 



this maimer they form a complete ring with the exeeption of a small anterior 

 portion of the circumferenee. They are interrupted by vascular canals and Ha- 

 ■ versian canals of tlie (la) differentiation. 



The central ring is composed of well developed Haversian systems separ- 

 ated here and there by short lameUse. The systems are small and large, but 

 well developed. Their lacuna^ are long and narrow. The systems are fre- 

 quently united by cross canals. The internal circumferential lamellfe form a 

 comi^lete ring of varying widths around the medullary canal. 



The femur of the orang-utan resembles the human femur more closely 

 than those of other apes or monkeys. 



Type I-III, la, C. 



LEFT FEMUR OF FELIS TIGRIS. TIGER. NO. 174981, U. S. NAT. MUS. 



Pl. 13, Fig. 221. Syn. Tab. VI 



Antero-posterior diameter of bone, 28 mm.; lateral, 22 mm. 



Antero-posterior diameter of medullary canal, 15 nun.; lateral, 12 mm. 



The medullary canal is full. Medullary index, 41%. 



Structure. — The posterior ridge is composed of well developed Haversian 

 systems. Beginning on both sides of the ridge and extending around the section 

 is a horseshoe band of lamellie with long lacunar and straight canaliculi, inter- 

 rupted by Haversian systems of the (la) differentiation. The central ring is 

 composed of well developed Haversian systems. The internal circumferential 

 lamellfe with long lacuna^ and straight canaliculi form a wide irregular ring 

 around the medullary canal. The ring is crossed by numerous radiating canals. 



Type I-III, la, C. 



BIGHT FEMUR OF HEMIGALUS HARDWICKI. CIVET CAT. NO. 32358, 

 AMER. MUS. NAT. HIST. 



Pl. 13, Fig. 222. Sy.v. Tab. VI 



Antero-posterior diameter of bone, 7 mm.; lateral, 5.5 mm. 



Antero-posterior diameter of medullary canal, 4.5 mm.; lateral, 3 mm. 



The medullary canal is full. Medullary index, 54%. 



Structure. — The three divisions are well marked. The external circum- 

 ferential lamellaj form a wide ring around the bone. It is crossed by canals 

 and interrupted by a few crude Haversian systems of tlie (la) differentiation. 

 Its lacunjE are long and the canaliculi are straight. The central ring is com- 

 posed of well developed Haversian systems with very little inter-Haversian 

 lamella'. The internal ciicuniferential lamella' form a narrow liiig around the 

 medullary canal. The lacuna- are long and tlie canjiliciili are straiglil. 



Type I-III, la, C. 



