NO. 3 



COMPARATIVE HISTOLOGY OF FEMUR FOOTE 



129 



Between the lamellae are some Haversian systems. The lacunas are oval and the 

 canaliculi are straight. The anterior and inner ridges are composed of a few 

 crude Haversian systems, lamina?, and branching canals. The anterior and 

 outer ridges have many more Haversian systems and relatively fewer canals 

 than the inner ridge. Between the three ridges the walls are composed of 

 laminae, interrupted by a few Haversian systems. The laminae are frequently 

 crossed by canals. Some cancellous bone appears on the medullary surfaces 

 of the anterior and posterior walls. 

 Type II-III, C. 



LEFT FEMUR OF A MULE. NO, 235, OR. MED. COLL. 



Pl. 16, Fig. 258. Syn. Tab. VI 



Antero-posterior diameter of bone, 65 mm. ; lateral, 51 mm. 

 Antero-posterior diameter of medullary canal, 38 mm.; lateral, 40 mm. 

 The medullary canal is full. Medullary index, 85%. 



Structure. — The posterior wall is over half cancellous. The posterior ridge 

 is composed of Haversian systems, inter-Haversian lamellae with oval lacunae 

 and many branching canals, having a direction toward the external surface of 

 the ridge. The remaining wall is composed of laminae, interrupted by Ha- 

 versian systems and crossed by numerous canals. In the outer wall near the 

 mid-line is a collection of Haversian systems forming a slight ridge. Around 

 the medullary canal in the anterior and lateral walls there are many spaces 

 of irregular shape which appear to be the result of senile changes. The lacuna' 

 are generally oval. 



Type II-III, C, senile. 



LEFT FEMUR OF A MULE. XO. 236, CR. MED. COLL. 



Pl. 16, Fig. 259. Syn. Tab. VI 



Antero-posterior diameter of bone, 61 mm. ; lateral, 50 mm. 

 Antero-posterior diameter of medullary canal, 40 mm. ; lateral, 38 mm. 

 The medullary canal is full. Medullary index, 100%. 



Structure. — The posterior ridge is composed of Haversian systems and 

 inter-Haversian lamellae with oval lacunae. There are many short, branching 

 canals having; a direction toward the external surface. About one-third of the 

 medullary portion of the wall is cancellous bone. The inner and anterior wall 

 is composed of laminae, interrupted by many Haversian systems. The systems 

 are more numerous around the medullary canal. Many cross canals appear 

 between the systems and extend across the laminae. The anterior half of the 

 outer wall is nearly all laminae which are interrupted by Haversian systems. 

 The posterior half is composed of irregular elongated Haversian systems and 



