NO. 3 COMPARATIVE HISTOLOGY OF FEMUR FOOTE 129 



Between the lamelte are some Haversiau systems. The lacunai are oval aud the 

 canalieuli are straight. Tlie anterior and inner ridges are composed of a few 

 crude Haversian systems, laminse, 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 (•()ni])osed of 

 laminje, interrupted by a few Haversian systems. The laminfe 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, CR. MED. COLL. 



Pl. 16, Fig. 258. Stk. 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 Haversiau systems, inter-Haversian lamella} with oval lacunae 

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

 tlie 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 lacunae 

 are generally oval. 



Type II-III, C, senile. 



LEFT FEMUR OF A MULE. NO. 236, CR. MED. COLL. 



Pl. 16, Pig. 359. Stn. 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 aud 

 inter-Haversian lamellae with oval lacuna. 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 Ha\-ersian systems. The systems 

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

 between the systems and extend across the lamina;. The anterior lialf of the 

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

 The posterior half is composed of irregular elongated Haversian systems and 



