NO. 3 



COMPARATIVE HISTOLOGY OF FEMUR FOOTE 



131 



Haversian systems of the (la) and (C) differentiations. The laminae, separated 

 and crossed by canals, form nearly the whole width of the outer, about one- 

 third of the anterior, and terminate somewhat abruptly at the junction of the 

 anterior and inner wall. The lacunas are oval and the canaliculi are straight. 



Underneath the laminar band is a central, irregularly shaped ring of Ha- 

 versian systems, very narrow in the outer, wider in the anterior, and forming 

 the whole of the inner and posterior wall. The systems are united by cross 

 canals and exhibit some senile changes. Their lacunae are oval and the cana- 

 liculi are straight. 



Around the medullary canal is a cancellous ring of lamellae. The bone is 

 composed of about equal parts of Haversian systems and laminae. The bone is 

 unusually hard. 



Type II-III, la, C. 



LEFT FEMUR OF GIRAFFA CAMELOPARDALIS. GIRAFFE. NO. 27752, AMER. MUS. NAT. HIST. 



Pl. 17, Fig. 262. Syn. Tab. VII 



Antero-posterior diameter of bone, 72 mm. ; lateral, 59 mm. 

 Antero-posterior diameter of medullary canal, 35 mm. ; lateral, 30 mm. 

 The medullary canal is full. Medullary index, 33%. 



Structure. — Beginning in the outer wall, close to the posterior ridge and 

 extending around the section to about the middle of the inner wall, is a wide 

 band of laminae, interrupted frequently by Haversian systems. The band forms 

 the external half of the posterior, all of the outer, and two-thirds of the anterior 

 and inner wall. The laminae are separated and crossed by canals. Their lacuna) 

 are well developed. 



The whole posterior, inner lateral, and medullary portions of the anterior 

 and posterior lateral wall are composed of Haversian systems with the excep- 

 tion of the internal circumferential lamella?. The systems vary somewhat in 

 size and are well developed. In the posterior wall they are separated by aggre- 

 gations of oval lacunae closely packed together. 



Internal circumferential lamellae with long lacunae and straight canaliculi, 

 widest in the outer wall, surround the medullary canal. 



Type II-III, C. 



LEFT FEMUR OF RHINOCEROS BICORNIS. RHINOCEROS. NO. 27757, 

 AMER. MUS. NAT. HIST. 



Pl. 17, Fig. 263. Syn. Tab. VII 



Antero-posterior diameter of bone, 47.5 mm. ; lateral, 130 mm. 

 Antero-posterior diameter of medullary canal, 14 mm. ; lateral, 23 mm. 

 The medullary canal is full. Medullary index, 55%. 



