NO. 3 



COMPARATIVE HISTOLOGY OF FEMUR FOOTE 



103 



composed of oval and long lacuna 1 with rather infrequent canaliculi. Here and 

 there, and especially in the posterior ridge, some lamina 1 have widened, short- 

 ened, and assumed in pari the shape of Haversian systems. 

 Type II-III, lb. 



RIGHT FEMUR OF A FETAL PIG, HALF FETAL PERIOD 8^ WEEKS. 



Pl. LI, Pig. 201. Syn. Tab. V 



Antero-posterior diameter of bone, 3.5 mm. ; lateral, 3 mm. 

 Antero-posterior diameter of medullary canal, 1.5 mm. ; lateral, 1 mm. 

 The medullary canal is situated eccentrically. The anterior wall is thin- 

 nest, the posterior thickest. 



The medullary canal is full. Medullary index, 17%. 



Structure. — The section is composed of concentric laminae separated and 

 crossed by wide canals. In the anterior wall the lamina? are short, in the lateral 

 wall, long, and in the posterior wall, irregular. There are no Haversian sys- 

 tems, although in the posterior wall the lamina? are very short and inclined to a 

 circular bend. The lacuna? are oval and the canaliculi are bushy. 



Type II. 



FEMUR OF CARIACCJS MACROTIS. DEER, OR. MED. COLL. 



Pl. 11, Fig. 202. Syn. Tab. V 



Antero-posterior diameter of bone, 25 mm. ; lateral, 24 mm. 

 Antero-posterior diameter of the medullary canal, 17 mm. ; lateral, 16.5 mm. 

 The medullary canal is full. Medullary index, 88%. 



Structure. — The bone is composed almost entirely of lamina 1 . They are 

 well developed, separated, and crossed by wide canals. Their lacuna 1 are long, 

 narrow, and completely developed and the canaliculi are long and branching. 

 Here and there are found a few aberrant Haversian systems, produced by a 

 circular widening of the concentric canals and the bending of a few lamella? 

 around the circular openings. The lamina? form the entire section, excepting 

 the posterior ridge and a small area near the anterior wall which are composed 

 of Haversian systems with many oval lacuna?. There are no distinct external 

 circumferential lamella?. The canals between the lamina? cross them at right 

 angles and communicate freely with each other. 



The internal circumferential lamina? form an irregularly shaped boundary 

 of the medullary canal. They are frequently crossed by canals extending out- 

 ward from the medullary canal. The surface of the posterior ridge shows the 

 tendon attachments of muscles. Extending from this surface to the internal 

 circumferential lamina 1 , and for a short distance on either side of the posterior 

 mid-line, is an area of Haversian systems. They are irregular in shape, well 



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