NO. 3 COMPARATIVE HISTOLOGY OF FEMUR FOOTE 197 



Structure. — The external circumferential lamella? are fra,ijmentary. The 

 central ring constitutes nearly all of the section and is composed of large, small, 

 and irregularly shaped Haversian systems in a wide band of lamellas, especially 

 in the inner and Y^osterior wall. The band is nearly displaced by Haversian 

 systems in the outer wall. Senile changes are frequent. The internal circum- 

 ferential lamella are fragmentary. The section shows an unusually large, 

 inner posterior ridge. 



Type I-III, C, senile. 



LEFT FEMUR OF A WHITE MALE. NO. 169, MED. UEPT. NORTHWESTERN UNIV. 



Pl. 33, Fig. 408. Syn. Tab. X 



Antero-posterior diameter of bone, 31 mm. ; lateral, 29 mm. 



Antero-posterior diameter of medullary canal, 16 mm.; lateral, 15 mm. 



The medullary canal is full. Medullary index, 37%. 



Structure. — Beginning on the inner side of the posterior ridge and extend- 

 ing around the inner lateral wall is a wide lamellar background in which are 

 numerous Haversian systems. In the anterior wall the band narrows to an 

 interrupted rim and widens again to a background in the outer wall. 



The central ring is composed of Haversian systems, large and small, with 

 some senile changes. Along the external surface of the posterior ridge the 

 systems are separated by lamella^ with oval and round lacunse. The internal 

 circumferential lamellie form a narrow ring around the medullary canal. Senile 

 changes are numerous in the systems in close proximity to the medullary canal. 



Type I-III, C, senile. 



RIGHT FEMUR OF A WHITE MALE, AGE 35. NO. 151, MED. DEPT. NORTHWESTERN UNrV. 



Pl. 32, Fig. 409. Syn. Tab. X 



Antero-posterior diameter of bone, 28 mm.; lateral, 31 mm. 



Antero-posterior diameter of medullary canal, 11.5 mm.; lateral, 12 mm. 



The medullary canal is full. Medullary index, 19%. 



Structure. — The external circumferential lamella; surround the bone. They 

 form thin bands in the lateral wall and are displaced by bone substance with 

 large oval lacuna; and bushy canaliculi in the posterior ridge. The anterior 

 wall is over half lamellsB, in which are parallel rows of crude Haversian systems 

 of the (la) differentiation, arranged concentrically. The lamellse and systems 

 form the external itart of the wall, and, as they approach and pass into the 

 lateral wall, they are replaced 1)y wide bands of irregularly shaped Haversian 

 systems. Senile changes are frequent in the inner lateral wall. Underneath 



