22 SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. 35 



The best type of human femui* is composed wholly of Haversian systems 

 of tlie complete differentiation. The systems have long, narrow lacunae, with 

 long, straight canaliculi situated between or within concentric lamellse which 

 enclose the Haversian canal. External and internal circumferential lamellae 

 form in some instances very narrow rings around the bone and medullary canal, 

 or they may be fragmentary. Such femora are not very common. 



Black race. — The femora of the black race exhibit types and combinations 

 of types ranging from a first and third to a complete third. The majority of 

 bones examined are type combinations. In some femora a wide horseshoe- 

 shaped band of lamellae, enclosing Haversian canals of the early incomplete 

 differentiation and a few, scattered, small Haversian systems, is found partly 

 surrounding a narrow, central ring of completely developed Haversian systems. 

 In others the horseshoe is narrower, and the central ring of Haversian systems 

 is wider; that is, the proportion of the horseshoe band to the Haversian ring is 

 a variable quantity. In still other femora the liorseshoe forms a fragmentary 

 background which can be distinguished, but which has been mostly displaced 

 by fully developed Haversian systems (pis. 21-23, figs. 306-324; pi. 25, figs. 

 335-340). 



The negro femur lias a higher medullary index tlian the white or Egyptian 

 race. 



During the examination of the right femur of negro No. 248674, U. S. Nat. 

 Mus., it was observed that considerably more than half of the section was first 

 type bone, in which were many Haversian canals of the primitive and incomplete 

 differentiation. It was then decided to examine all of the long bones of that 

 negro in order to ascertain, if possible, whether or not the structure was basic 

 in character. Accordingly, the left femur, tibia, fibula, radius, ulna, humerus, 

 clavicle, and metatarsal bone of the great toe were examined. The result was 

 they were all found to conform closely to what was found in the right femur. 

 It was therefore concluded that the type combination found in the femur was 

 a representative type of the whole long bone formation of that particular negro, 

 and that one type or type combination would probably not be found in one 

 bone of an individual and a different one in another (pi. 24, figs. 325-333). 



The yelloiv-broivn race. — With one exception these femora were pre-Colum- 

 ))iaii. They were a little smaller than those of the blacks. The majority were 

 conii)osed of second and third, and first, second, and third type combinations. 

 Only three or four were pure third type. In the femora, composed of type com- 

 binations, there was a greater average proportion of first type bone than was 

 present in the other races examined. 



The medullary canals were relatively larger than in the other races, as may 

 be seen from their medullary indices — yellow-brown 43.8%, blacks 41.9%, 

 Egyptians 39.5%, and whites 38.57^. Therefore the yellow-brown femur has 



