130 



SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



vol. 35 



of laminae. The femur of the mule differs from the horse in its predominating 

 proportion of laminae and in the frequent senile changes present in its scattering 

 Haversian systems. The difference between the horse and the mule is found in 

 the jackass. 



Type II-III, C. 



LEFT FEMUR OF ELEPHAS INDICUS. ASIATIC ELEPHANT. AMER. MUS. NAT. HIST. 



Pl. 17, Fig. 260. Syn. Tab. YII 



Antero-posterior diameter of bone, 121 mm. ; lateral, 77 mm. 

 Antero-posterior diameter of medullary canal, 50 mm. ; lateral, 38 mm. 

 The medullary canal is full. Medullary index, 25%. 



Structure.-— The section is composed of lamellae, laminae, and Haversian 

 systems, the laminae predominating. The posterior ridge is composed of Ha- 

 versian systems with inter-Haversian lamellae. Beginning in the inner side of 

 the ridge and extending around the external surface of the posterior inner wall 

 is a wide band of lamellae, frequently interrupted by Haversian systems. The 

 lamellae soon separate into laminae as they extend around the section. The 

 laminae, frequently interrupted by Haversian systems and crossed by canals, 

 complete the circumference of the bone to the posterior ridge. In the anterior 

 wall they constitute two-thirds, in the inner wall one-third, and in the outer 

 and posterior wall over half the width of the wall. As they approach the ridge 

 they shorten and widen into elongated Haversian systems. Thus a wide horse- 

 shoe of lamellae and laminae surrounds the bone. In the anterior wall the toe 

 of this shoe is very narrow, having 1 been displaced by Haversian systems. The 

 lacunae and canaliculi are well developed. Underneath the laminar shoe is an 

 irregularly shaped central ring of well developed Haversian systems with some 

 senile changes around the medullary canal The lacunae are well developed. 

 Around the medullary canal is an enclosing ring of lamellae in the form of 

 cancellous bone. 



The bone is over half laminae and lamellae, and exhibits a different type of 

 structure from that seen in the African elephant. 

 Type II-III, C, senile. 



RIGHT FEMUK OF HIPPOPOTAMUS AMPHIBUS. HIPPOPOTAMUS 



Pl. 17, Fig. 361. Syn. Tab. VII 



Antero-posterior diameter of bone, 70 mm. ; lateral, 70 mm. 

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

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



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

 ing around the bone to the inner wall is a wide band of laminae, interrupted by 



