NO. 6 COMPARATIVE HISTOLOGY OF FEMUR FOOTE 187 



LEFT FEMUR OF A WHITE MALE, AGE 50. NO. 10, MED. DEPT. NORTHWESTERN X'NIV. 



Pl. 29, Fig. 380. Syn. Tab. X 



Antero-posterior diameter of boue, 30 mm.; lateral, 31.5 mm. 



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



The medullary canal is full. Medullary index, 20%. 



Structure. — The external circumferential lamellae appear only in short frag- 

 ments. The central ring is composed of large, small, and irregular Haversian 

 systems with many senile changes. The internal circumferential lamellae form 

 a narrow ring around the medullary canal. 



Type III, C, senile. 



FEMUR OF A SENILE WHITE AMERICAN FEMALE, AGE 52. NO. 227876, U. S. NAT. MUS. 



Pl. 29, Pig. 381. Syn. Tab. X 



Antero-posterior diameter of bone, 22 mm. ; lateral, 25 mm. 



Antero-posterior diameter of medullary canal, 13.5 mm.; lateral, 12 mm. 



The medullary canal is full. Medullary index, 42%. 



There is a difference of eight years between tlie senile femora of figures 381 

 and 382. Tlie two femora have about the same external diameter, but figure 381 

 has an index of 42%, and figure 382, 74%. 



Structure. — Femur (fig. 381) is of a slightly luwer type of structure than 

 figure 382. This may be seen by the concentric arrangement of the oblong Ha- 

 versian systems of tlie inner wall. The external circumferential lamellae are 

 fragmentary. The central ring is composed of large and small Haversian sys- 

 tems in different stages of senility. A few are normal; that is, their Haversian 

 canals are about the usual size. Some have large Haversian canals and crescent- 

 shaped lamelte; some have large canals and narrow rings of granular lamellae; 

 some have large canals and perfectly black, opaque rings or crescents around 

 tlieni; and some are entirely gone. 



The internal circumferential lamellfP are fragmentary. 



Type III, C, senile. 



FEMUR Ol'' A SENILE WHl'l'E FEMALE, AGE 60. NO. 227880, V. S. NAT. MUS. 



Pl. 2:1, Fig. 382. Syn. Tab. X 



Antero-posterloi' diainetcr of bone, 24 nniL ; hderal, 25 nun. 



Antero-posterior diamett'i- of medullary canal, 16 mm.; lateral, 16 mm. 



Cancellous bone is present in places. Tlie bone is extremely soft, light, and 

 lliin walled. The medullary canal is relatively large. In tlie wall of the bone 

 are large, irregularly shaped spaces. 



The medullary canal is full. Medullary index, 74%. 



