NO. 3 



COMPARATIVE HISTOLOGY OF FEMUR FOOTE 



11!) 



RIGHT FEMUR OF THYLACINUS CYNOCEPHALUS. TASMANIAN WOLF 



Pl. 14, Pig. 237. Syx. Tab. VI 



Antero-posterior diameter of bone, 19.5 mm.; lateral, 15 mm. 

 Antero-posterior diameter of medullary canal, 8 mm.; lateral, 8.5 mm. 

 The medullary canal is full. Medullary index, 28%. 



Structure. — The section is surrounded by a narrow ring of external lamellae, 

 interrupted here and there by crude Haversian systems of the (la) differen- 

 tiation. Underneath this ring is a wide horseshoe of lamella 1 , interrupted by 

 many crude Haversian systems of the (la) differentiation arranged concen- 

 trically. The outer wall is all lamella 1 . 



Underneath this band is a central, incomplete ring of well developed Ha- 

 versian systems with inter-Haversian lamellae. In the posterior wall the sys- 

 tems form nearly the whole of the wall. Here the oval large lacunas with 

 bushy canaliculi are pronounced. 



Internal circumferential lamellae form a narrow ring around the medullary 

 canal. Their lacunae are long. 



Type I-III, la, C. 



RIGHT FEMUR OF DASYPROCTA AGOUTI. NO. 15669, AMER. M US. NAT. HIST. 



Pl. 14, Fig. 238. Syn. Tab. VI 



Antero-posterior diameter of bone, 10 mm.; lateral, 8 mm. 

 Antero-posterior diameter of medullary canal, 6.5 mm.; lateral, 5 mm. 

 The medullary canal is full. Medullary index, 93%. 



Structure. — The three divisions are well marked. A wide ring of external 

 circumferential lamella 1 , interrupted by crude Haversian systems of the (la) 

 differentiation and crossed by canals, surrounds the section with the exception 

 of the posterior ridge. The lamellar ring forms more than half of the section. 

 The central ring is composed of well developed Haversian systems with inter- 

 Haversian lamella 1 . 



The systems of the central ring reach the surface at the posterior ridge 

 where they are separated by bone substance with oval lacunae. The internal 

 circumferential lamellae form a narrow ring around the medullary canal. The 

 lacunae are long in the external and internal lamellae; elsewhere they are oval. 



Type I-III, la, C. 



LEFT FEMUR OF LASIOPYGA CENTRALIS JOHNSTONI. AFRICAN MONKEY. NO. 27705, 



AMER. MUS. NAT. HIST. 



Pl. 14. Fig. 2.'!!). Syn. Tab. VI 



Antero-posterior diameter of bone, 9 mm. ; lateral, 8 mm. 

 Antero-posterior diameter of medullary canal, 5.5 mm.; lateral, 5 mm. 



9 



