NO. 3 COMPARATIVE HISTOLOGY OF FEMUR FOOTE 159 



Antero-posterior diameter of medullary canal, 24 mm. ; lateral, 15 mm. 



The medullary canal is full. Medullary index, 92%. 



Structure. — A wide circumferential horseshoe of lamellae surrounds the 

 section. It gradually increases in width in the inner and outer, and constitutes 

 nearly the whole of the anterior wall. It is interrupted by Haversian systems 

 of the (la) and (C) differentiations. The central ring is composed of Ha- 

 versian systems of varying sizes. The communicating canals between the sys- 

 tems are few. There seems to be great variation in the different femora in this 

 respect, and their variation affords a possible explanation of senile changes in 

 bone. Near the medullary canal the senility is marked. The Haversian sys- 

 tems here are practically gone. The wall of the bone, including the posterior 

 ridge, is very thin. The internal circumferential lamellfe are fragmentary. 

 The senile changes are much more pronounced than in the left femur and 

 may be the result of disuse. 



Type I-III, la, C, senile. 



LEFT FEMUR OF A NEGRESS. AGE 14. NO. 226, CR. MED. COLL. 



Pl. 23, EiG. 323. Stn. Tab. VIII 



The mother is white and the father is not a pure black. The child died 

 from the effects of carbolic acid taken for suicidal purposes. The upper third 

 of the femur has a very small medullary canal. 



Antero-posterior diameter of bone, 24 mm.; lateral, 18 mm. 



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



The medullary canal is full. Medullary index, 34%. 



Structure. — The posterior ridge is thick and composed of irregularly shaped 

 Haversian systems, separated in the circumferential portion by bone substance 

 with round and oval lacunte and bushy canaliculi. Numerous canals surrounded 

 by clear areas appear. The external circumferential lamellse form an enclosing 

 ring. The central ring is composed of Haversian systems, which are oval and 

 round in cross-section and separated in places by short laminse. Their lacunae 

 are generally oval; otherwise the systems are fairly well developed. The in- 

 ternal circumferential lamellae are fragmentary, excepting in the inner wall 

 where they form a wide crescent. The bone is not quite complete. 



Type I-III, C. 



FEMUR OF A NEGRO. NO. 1, MED. DEPT. TULANE UNIV. 



Pl. 23, Fig. 323. Stn. Tab. VIII 



Antero-posterior diameter of bone, 23 mm. ; lateral, 25 mm. 

 Antero-posterior diameter of medullary canal, 11 mm.; lateral, 10 mm. 

 The medullary canal is full. Medullary index, 24%. 



