NO. 3 . COMPARATIVE HISTOLOGY OF FEMUR FOOTE 211 



Structure. — The external circumfereutial lamellse are fragmentary. The 

 central ring constitutes nearly all of the section and is composed of Haversian 

 systems exhibiting many senile changes. 



Internal circumferential lamelte surround the medullary canal. 



Type III, C, senile. 



* RIGHT FEMUR OF A WHITE MALE. NO. 287, CR. MED. COLL. 



Stn. Tab. XI 



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



Antero-posterior diameter of medullary canal, 12 mm. ; lateral, 9 mm. 



The medullary canal is full. Medullary index, 21%. 



Structure. — Around the outer and anterior wall is a wide band of lamellie, 

 interrupted by Haversian systems of the (la) differentiation. The band is 

 displaced in the inner wall by Haversian systems. The central ring constitutes 

 all of the inner wall, the posterior ridge, two-thirds of the outer and one-third 

 of the anterior wall. It is composed of Haversian systems of the (C) dif- 

 ferentiation, large and small, separated in the outer wall by wide inter-Ha- 

 versian lamelte. Some senile changes occur. The internal circumferential 

 lamellffi form a narrow ring around the medullary canal. 



Type I-III, la, C, senile. 



* EIGHT FEMUR OF A WHITE MALE. NO. 288, CR. MED. COLL. 



Syn. Tab. XI 



Antero-posterior diameter of bone, 30 mm. ; lateral, 31 mm. 



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



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



Structure. — A narrow ring of external circumferential lamellae surrounds 

 the section. 



The central ring constitutes nearly all of the bone and is composed of Ha- 

 versian systems, many of which are senile. The systems are united by cross 

 canals. 



A narrow ring of internal circumferential lamellae surrounds the medul- 

 lary canal. 



Type III, C, senile. 



RIGHT FEMUR OF A WHITE MALE. NO. 289, CR. MED. COLL. 



PL. 35, Fig. 451. Syn. Tab. XI 



Antero-posterior diameter of bone, 30 mm.; lateral, 33 mm. 

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

 The medullary canal is full. Medullary index, 27%. 



