NO. 6 COMPARATIVE HISTOLOGY OF FEMUR FOOTE 149 



XL MAN 



One hundred and tbirty-iiiue femora were examined. 



General Character of the Femuk 



The femur of man presents a variety of sliapes. 



The medulhuy canals are generally full of eaufellous bone, the meshes of 

 which are filled with marrow. Tlie medullary surfaces are almost always 

 rough, Imt in some round sections the surfaces are smooth and cancellous 

 bone is absent. 



The average medullary index of the adult is .38.6%. Comparing the aver- 

 age index of man witli tliat of other mammals, which is 63.3%, it will be noticed 

 that the medullary canal is proi^ortiouately smaller and the wall of the bone 

 thicker in man than in other mammals, or in bipeds than in (|uadrupeds. 



The following types and comljinations of types arc t'diiiid: the third, first 

 and third, second and third, and first, second, and third. The third type occurs 

 in the (la), (lb), and (C) forms of ditferentiation. The jture third type bone 

 without senile changes is rather infrequent. The human series consists of the 

 fetal, infantile, adolescent, and adult femora. Tlie fetal series includes the 

 white and black races ; the infantile, the j'ellow-brown, ancient Egyptian, and 

 modern white races; the adolescent, the yellow-brown, ancient Egyptian, and 

 white races ; and the adult, all races. 



Fetal Humax Femora 



Seven femora were examined. 



In the very young fetus of two to three montlis, l)asic Ixme substance is 

 present and is marked oft" into regular areas by crude, In-anching canals. As 

 fetal life advances the canals become less branching and more concentric. Grad- 

 ually the basic bone becomes lamellated and then develops into tlie second type 

 and remains so until birth. Throughout childhood and youth the lamina tend 

 to disappear and to be replaced by Haversian systems, until the bone develop- 

 ment is completed. 



In the formation of human fetal femora the following plan was observed. 

 A horseshoe-shaped band of lamellje or laminae with o\al lacunae and bushy 

 canaliculi is formed around the medullary canal, with tlie exception of tlie pos- 

 terior ridge which appears to have an independent formation at a later date. 

 As the bone develops the ridge fuses with the lateral wall. 



eight femur OF A WHITE FETUS, TWO AXD OXE-HALF MOXTHS OLD 



Pl. 21. Fig. 299. Six. Tab. YIII 

 Antero-posterior diameter of bone, 1.8.; lateral, 1.5 mm. 

 Antero-posterior diameter of medullary canal, 0.5 mm.; lateral, 0.-4 mm. 

 The medullary canal is full. Medullary index, 8%. 



