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SMITHSONIAN CONTEIBUTIONS TO KNOWLEDGE 



vol. 35 



crossed by radiating canals and interrupted by crude Haversian canals. Tbe 

 lamellae on reaching the anterior wall separate into lamina?, which constitute 

 the whole inner wall. Here and there the canals between the lamina? widen 

 into circular openings. The posterior ridge is composed of Haversian systems, 

 between which are short lamella? with round lacuna?. The internal circum- 

 ferential lamella? surround the medullary canal. 

 Type I-II-III, la, C. 



FEMUR OE A FOX TERRIER (NOT A PUKE BLOOD). NO. 202, CR. MED. COLL. 



Pl. 19, Fig. 281. Syn. Tab. VII 



Antero-posterior diameter of bone, 11 mm. ; lateral, 9.5 mm. 

 Antero-posterior diameter of medullary canal, 6.5 mm. ; lateral, 6 mm. 

 The medullary canal is full. Medullary index, 59%. 



Structure. — The section is surrounded by a wide horseshoe of lamina? which 

 forms three-fourths of the thickness of the wall of the hone. The canals between 

 the lamina? widen at intervals into circular areas. The lamina? are frequently 

 crossed by irregular canals. The lacuna? are oval. The central ring is a nar- 

 row crescent and is composed of well developed Haversian systems. The ring 

 reaches the surface of the posterior ridge where it is composed of vascular 

 canals surrounded by concentric lamella?. Between the canals are long, minute, 

 tendon insertions. The internal circumferential lamella? form a narrow ring 

 around the medullary canal. Just behind the ring are several large vascular 

 spaces. 



Type II-ni, C. 



RIGHT FEMUR OF A MONGREL DOG (NO CHARACTERISTIC FEATURES). 

 NO. 200, CR. MED. COLL. 



Pl. 19, Fig. 282. Syn. Tab. VII 



Antero-posterior diameter of bone, 12.5 mm. ; lateral, 13 mm. 

 Antero-posterior diameter of medullary canal, 8.5 mm. ; lateral, 9 mm. 

 The medullary canal is full. Medullary index, 90%. 



Structure. — The section is surrounded by a horseshoe band of lamina? and 

 lamella?. The lamina? form the whole width of the inner wall. They then be- 

 come fewer in number as they reach the anterior wall, where they are reduced 

 to a narrow lamellar band. The lamella? then widen and separate into lamina? 

 as the band reaches the posterior ridge. The central ring is reduced to a long, 

 narrow crescent of Haversian systems which nearly encircles the section. The 

 systems reach the surface of the posterior ridge and form nearly the whole 

 width of the posterior wall. They are well developed. The internal circum- 

 ferential lamella? do not form an enclosing ring. In the posterior wall they 

 form a narrow band, in the outer wall the band widens into lamina?, and in the 



