NO. 3 COMPARATIVE HISTOLOGY OF FEMUR FOOTE 205 



later; and some the latest. The lacunae are generally oval. A narrow ring of 

 internal circumferential lamellae surrounds the medullary canal. 

 Type III, C, senile. 



* LEFT FEMUR OF A WHITE MALE, AGE 50. NO. 268, CR. MED. COLL. 



Syn. Tab. XI 



Antero-posterior diameter of bone, 30 mm. ; lateral, 30 mm. 



Antero-posterior diameter of medullary canal, 13 mm. ; lateral, 12 mm. 



Medullary index, 21%. 



Structure. — The external circumferential lamellae are fragmentary. The 

 section is composed almost entirely of small, large, and irregularly shaped Ha- 

 versian systems and a small amount of inter-Haversian lamellae. In the vicinity 

 of the medullary canal many of the systems are senile. The internal circum- 

 ferential lamellae are fragmentary. 



Type III, C, senile. 



* RIGHT FEMUR OF A WHITE MALE. NO. 269, CR. MED. COLL. 



Syn. Tab. XI 



Antero-posterior diameter of bone, 29 nnn. ; lateral, 33.5 mm. 



Antero-posterior diameter of medullary canal, 17 mm.; lateral, 20 mm. 



Medullary index, 54%. 



Structure. — A wide background of lamelliB, enclosing Haversian canals and 

 small Haversian systems, forms the external half of the anterior wall and is 

 mostly displaced by Haversian systems as it extends around the lateral wall 

 to the posterior ridge. The systems vary in size and shape and many show 

 senile changes. There is a scarcity of communicating cross canals. 



In the inner wall a short, fan-shaped band of laminae, interrupted by small 

 Haversian systems, extends from the medullary surface of the posterior ridge 

 outward. This has been observed in a number of femora, but not in all. Its 

 significance is not clear. 



The internal circumferential lamellae form a very narrow fragmentary ring 

 around the medullary canal. 



Type I-II-III, la, C, senile. 



* RIGHT FEMUR OF A WHITE MALE. NO. 270, CR. MED. COLL. 



Stn. Tab. XI 



Antero-posterior diameter of bone, 31 mm.; lateral, 25 mm. 

 Antero-posterior diameter of medullary canal, 14 mm. ; lateral, 13 mm. 

 Medullary index, 29%. The section is almost quadrangular in shape. 



