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SMITHSONIAN" CONTRIBUTIONS TO KNOWLEDGE 



vol. 35 



Structure. — A wide horseshoe band of lamellae and laminae, interrupted 

 by Haversian systems of the (la) and (C) differentiations, surrounds the sec- 

 tion. The band is narrow in the inner wall. The central ring is narrow and 

 irregular and composed of Haversian systems and inter-Haversian lamellae. 



Internal circumferential lamellae form an irregular ring around the medul- 

 lary canal. In the inner wall they extend outward in an oblique direction and 

 are separated by canals having the same direction. 



Type I-II-III, la, C. 



BIGHT PEMUB OF A NEGBO. NO. 8, MED. DEPT. TULANE UNIV. 



Pl. 25, Fig. 339. Syn. Tab. VIII 



Antero-posterior diameter of bone, 27 mm. ; lateral, 25 mm. 



Antero-posterior diameter of medullary canal, 12.5 mm.; lateral, 9 mm. 



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



Structure. — On both sides of the posterior ridge are two wide external 

 bands of lamellae of unequal length. They are interrupted by small, crude 

 Haversian canals of the (la) differentiation. The band of the inner increases 

 in width as it reaches the anterior wall where it forms nearly the whole wall. 

 It is then displaced by Haversian systems. The band of the outer wall is 

 much shorter and is displaced by Haversian systems about the middle of the 

 wall. The lacunae are generally long. The Haversian systems of the section 

 occupy irregularly shaped areas. The internal circumferential lamellae form a 

 wide ring around the medullary canal and it is crossed by frequent canals. 



Type I-III, la, C. 



LEFT FEMUB OF A NEGBO. NO. 7, MED. DEPT. TULANE UNIV. 



Pl. 25, Fig. 340. Syn. Tab. IX 



Antero-posterior diameter of bone, 30 mm. ; lateral, 26 mm. 

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

 The medullary canal is full. Medullary index, 50%. 



Structure. — The external circumferential lamellae are fragmentary. The 

 central ring constitutes practically the whole bone, and is composed of Ha- 

 versian systems which show extensive senility. Around the medullary canal 

 many systems have entirely disappeared, leaving irregularly shaped spaces. 



The internal circumferential lamellae form a narrow ring around the medul- 

 lary canal. 



Type III, C, senile. 



