156 SMITHSONIAX CONTRIBUTIONS TO KNOWLEDGE VOL. 35 



Structure. — The external circumfereiitial lamellfe are fragmentary. The 

 central ring is composed of well developed Haversian systems. A narrow ring 

 of internal circumferential lamellae surrovinds tlie medullary canal. 



Type III, C. 



LEFT FEMUR OF A NEGRO. NO. 10, MED. DEPT. TULANE UNIV. 



Pl. 22, Fig. 313. Syn. Tab. VIII 



Antei'o-posterior diameter of bone, 26 mm. ; lateral, 29 mm. 



Antero-posterior diameter of medullary canal, 14 mm. ; lateral, 15 mm. 



The medullary canal is full. Medullary index, 38%. 



Structure. — The section is composed of a wide background of the lamellar 

 horseshoe occupying the lateral wall. The lamella; are frequently interrupted 

 by Haversian systems of the (C) differentiation. In the anterior wall the 

 lamellae are replaced by Haversian systems. 



The remainder of the section is composed of well develoised Haversian sys- 

 tems. Cancellous bone surrounds the medullary canal. 



Type I-III, C. 



RIGHT FEMITR OF A FEMALE NEGRO. AGE 40. NO. 123, MED. DEPT. TULANE UNIV. 



Pl. 22, Fig. 314. Syn. Tab. VIII 



Antero-posterior diameter of bone, 28 mm. ; lateral, 27 mm. ' 



Antero-i3osterior diameter of medullary canal, 14 mm. ; lateral, 11 mm. 



The medullary canal is full. Medullary index, 25%. 



Structure. — The external circumferential lamellie appear only in fragments. 

 The central ring, which constitutes most of the bone, is composed of Haversian 

 systems, many of which are senile. The internal circumferential lamella form 

 a narrow ring around the medullary canal. The lacunae of all units are oval 

 and long and the canaliculi are straight. 



Type III, C, senile. 



LEFT FEMUR OF A NEGRO. AGE 40. NO. 79, MED. DEPT. TULANE UNIV. 



Pl. 22, Fig. 3 15. Syn. Tab. VIII 



Antero-posterior diameter of bone, 30.5 mm. ; lateral, 26.5 mm. 



Antero-posterior diameter of medullary canal, 17 mm.; lateral, 15 mm. 



The medullaiy canal is full. Medullary index, 46%. 



Structure. — The external circumferential lamellas a^jpear only in fragments. 

 The central ring forms most of the section and is composed of Haversian sys- 

 tems. Around the medullary region nearly half of the wall of the bone is com- 

 posed of Haversian systems in an extremely senile condition. The systems of 



