NO. 3 COMPAHATIVE HISTOLOGY OF FEMUR FOOTE 189 



Structure. — External circumferential lamella? surround the section. In the 

 inner and anterior wall they are interrupted by crude Haversian systems of 

 the (la) differentiation. 



The central ring is composed of large, small, aiul irregularly shaped, well 

 developed Haversian systems. Here and there a few, short, inter-Haversian 

 lamelte appear. Some of the systems are senile. But, on the whole, the Ha- 

 versian systems are strong and well developed. 



The internal circumferential lamella; form a narrow ring around the medul- 

 lary canal. 



Type III, la, C. 



LEFT FEMUR OF AN EAST INDIAN. NO. 223, CR. MED. COLL. 



Pl. 30, Fig. 387. Syn. Tab. X 



The leg had been amputated below the knee and the femur had not exercised 

 its normal function for years. 



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



Antero-posterior diameter of medullary canal, 17 mm. ; lateral, 12 mm. 



The medullary canal is full. Medullary index, 49%. 



Structure. — The section is surrounded by external circumferential lamellae, 

 thinnest in the anterior wall. The lamellae are interrujited by crude Haversian 

 systems of the (la) differentiation. 



The central ring is composed of large, small, and irregularly shaped Ha- 

 versian systems, showing senile changes which are most numerous around the 

 medullary canal. 



Internal circumferential lamellae form a narrow ring around the medullary 

 canal. 



Type III, la, C, senile. 



A comparison of the two foregoing femora shows that the femur of the 

 amputated leg is smaller than the other, the index is higher, the wall of the 

 bone is thinner, and senile changes are more marked. 



RIGHT FEMUR OF A WHITE MALE, AGE 55. NO. 228479, U. S. NAT. MUS. 



Pl. 30, Fig. 388. Syn. Tab. X 



Antero-posterior diameter of bone, 32 nun. ; lateral, 28 mm. 



Antero-posterior diameter of medullary canal, 14 uini.; lateral, 17 mm. 



Tlie medullary canal is full. Medullary index, 36%. There is considerable 

 cancellous bone. 



Structure.— -The external circumferential lamella are fragmentary and 

 sho^\' the remains of the lamellar or laminar horseshoe. 



