NO. 3 



COMPARATIVE HISTOLOGY OF FEMUR FOOTE 



181 



Beginning' on either side of this ridge and extending completely around the 

 bone is a very wide horseshoe-shaped band of lamellae with long lacunae and 

 straight canaliculi. It forms more than half the thickness of the wall of the 

 bone. It is perforated at frequent intervals by irregularly shaped spaces or 

 openings, surrounded by very narrow rims of lamellae. The openings are more 

 numerous in the inner wall where they take a concentric arrangement. Between 

 the openings are Haversian systems which are wide apart in the inner and close 

 together in the outer wall. The lamellae are clearly marked, their lacunae are 

 long and oval and the canaliculi are very numerous, long, and branching. The 

 Haversian systems are well developed. 



This wide lamellar band is distinctly distinguished from the narrow, cen- 

 tral ring of Haversian systems underneath. The systems are somewhat irregu- 

 lar in shape, but well developed. In all of them the canaliculi are extremely 

 numerous. The internal circumferential lamellae surround the medullary canal. 

 They form a thick band in the inner wall, a narrower band in the outer, and 

 a narrow rim in the anterior and posterior wall. 



The bone, therefore, has three concentric rings in section, an extremely 

 wide lamellar ring over half the thickness, a narrow central Haversian ring 

 one-fourth the thickness, and an irregular ring of internal circumferential 

 lamellae. 



Type I-III, lb, C, senile. 



RIGHT FEMUR OF AN ANCIENT EGYPTIAN. NO. 258675(e), U. S. NAT. MUS. 



Pl. 28, Fig. 369. Syn. Tab. IX 



Antero posterior diameter of bone, 26 mm.; lateral, 21.5 mm. 



Antero-posterior diameter of medullary canal, 14 mm.; lateral, 10 mm. 



The medullary canal is full. Medullary index, 44%. 



The bone is chalky. The femur is pear-shaped in cross-section. 



Structure. — The posterior ridge is composed of large, uniformly developed 

 Haversian systems and large, vascular canals surrounded by a few concentric 

 lamellae. 



Beginning on both sides of the ridge and extending around the section is 

 a wide horseshoe of lamella; with long lacunae and straight canaliculi, frequently 

 interrupted by Haversian systems. The toe of the shoe forms nearly all of the 

 anterior, and the heel, half of the posterior wall. The lacunae are long, nar- 

 row and oval and their canaliculi are long and closely branching. Underneath 

 the horseshoe, between it and the internal circumferential lamellae, is an irregu- 

 larly shaped crescent of Haversian systems situated eccentrically. 



The internal circumferential lamellae surround the medullary canal. 



In the inner wall the internal lamellae widen abruptly and occupy one- 

 third of the width of the wall. In the anterior, outer, and posterior wall they 



