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SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



VOL. 35 



developed for the most part, separated by bone substance with oval lacuna? 

 and bushy canaliculi, and surrounded by a coarse network of canals. Their 

 lacuna? are long and narrow, generally. A few, however, show round or oval 

 lacunae with short, bushy canaliculi. The bone is uniform. 

 Type n-III, C. 



FEMUR OF SUS. DOMESTIC PIG. CR. MED. COLL. 



Pl. 11, Fig. 203. Syn. Tab. V 



Antero-posterior diameter of bone, 21.5 mm. ; lateral, 18.5 mm. 

 Antero-posterior diameter of medullary canal, 16.5 mm. ; lateral, 12.5 mm. 

 The medullary canal is full. Medullary index, 108%. 



Structure. — The bone, with the exception of the posterior wall, is composed 

 of concentric lamina?. The lamina? are separated and crossed by wide canals 

 which frequently communicate with each other. The separating canals, here 

 and there, widen into circular areas which are surrounded by incompletely 

 developed concentric lamella? and form aberrant Haversian systems. The lami- 

 na? are long or short and strongly developed. They have long, narrow lacuna? 

 and branching canaliculi. In the posterior wall are two areas of well developed 

 Haversian systems separated by an intermediate wall of lamina?. These are 

 tli e only regular systems of the section. 



The femur of the adult pig is second type with two areas of Haversian 

 systems in the posterior wall. This bone, therefore, is essentially second in 

 type as it emerges from the fetal stage, and, for the most part, remains second 

 in the adult. 



Type 11-111, C. 



RIGHT FEMUR OF SUS SCROFA. WILD BOAR. (ARKANSAS.) OR. MED. COLL. 



Pl. 11, Fig. 201. Syn. Tab. V 



Antero-posterior diameter of bone, 23 mm. ; lateral, 20 mm. 

 Antero-posterior diameter of medullary canal, 15 mm. ; lateral, 13 mm. 

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



Structure. — The bone is composed of concentric lamina? crossed and divided 

 into short segments by canals. The lamina? are composed of lamella? with long 

 narrow lacuna? and straight canaliculi. 



In the posterior wall are two ridges separated by the intervening portion 

 of the posterior wall. These ridges are composed of well developed Haversian 

 systems which occupy the whole thickness of the wall from the external lamina? 

 to the internal. Between the ridges the posterior wall is composed of lamina? 

 alternating with Haversian systems in concentric rows. About the middle of 

 the lateral walls on both sides of the two riclges, crude Haversian systems are 



